drivers/media/video/ov7670.c

/*
 * A V4L2 driver for OmniVision OV7670 cameras.
 *
 * Copyright 2006 One Laptop Per Child Association, Inc.  Written
 * by Jonathan Corbet with substantial inspiration from Mark
 * McClelland's ovcamchip code.
 *
 * This file may be distributed under the terms of the GNU General
 * Public License, version 2.
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/videodev.h>
#include <media/v4l2-common.h>
#include <linux/i2c.h>


MODULE_AUTHOR("Jonathan Corbet <corbet@lwn.net.");
MODULE_DESCRIPTION("A low-level driver for OmniVision ov7670 sensors");
MODULE_LICENSE("GPL");

/*
 * Basic window sizes.  These probably belong somewhere more globally
 * useful.
 */
#define VGA_WIDTH	640
#define VGA_HEIGHT	480
#define QVGA_WIDTH	320
#define QVGA_HEIGHT	240
#define CIF_WIDTH	352
#define CIF_HEIGHT	288
#define QCIF_WIDTH	176
#define	QCIF_HEIGHT	144

/*
 * The 7670 sits on i2c with ID 0x42
 */
#define OV7670_I2C_ADDR 0x42

/* Registers */
#define REG_GAIN	0x00	/* Gain lower 8 bits (rest in vref) */
#define REG_BLUE	0x01	/* blue gain */
#define REG_RED		0x02	/* red gain */
#define REG_VREF	0x03	/* Pieces of GAIN, VSTART, VSTOP */
#define REG_COM1	0x04	/* Control 1 */
#define  COM1_CCIR656	  0x40  /* CCIR656 enable */
#define REG_BAVE	0x05	/* U/B Average level */
#define REG_GbAVE	0x06	/* Y/Gb Average level */
#define REG_AECHH	0x07	/* AEC MS 5 bits */
#define REG_RAVE	0x08	/* V/R Average level */
#define REG_COM2	0x09	/* Control 2 */
#define  COM2_SSLEEP	  0x10	/* Soft sleep mode */
#define REG_PID		0x0a	/* Product ID MSB */
#define REG_VER		0x0b	/* Product ID LSB */
#define REG_COM3	0x0c	/* Control 3 */
#define  COM3_SWAP	  0x40	  /* Byte swap */
#define  COM3_SCALEEN	  0x08	  /* Enable scaling */
#define  COM3_DCWEN	  0x04	  /* Enable downsamp/crop/window */
#define REG_COM4	0x0d	/* Control 4 */
#define REG_COM5	0x0e	/* All "reserved" */
#define REG_COM6	0x0f	/* Control 6 */
#define REG_AECH	0x10	/* More bits of AEC value */
#define REG_CLKRC	0x11	/* Clocl control */
#define   CLK_EXT	  0x40	  /* Use external clock directly */
#define   CLK_SCALE	  0x3f	  /* Mask for internal clock scale */
#define REG_COM7	0x12	/* Control 7 */
#define   COM7_RESET	  0x80	  /* Register reset */
#define   COM7_FMT_MASK	  0x38
#define   COM7_FMT_VGA	  0x00
#define	  COM7_FMT_CIF	  0x20	  /* CIF format */
#define   COM7_FMT_QVGA	  0x10	  /* QVGA format */
#define   COM7_FMT_QCIF	  0x08	  /* QCIF format */
#define	  COM7_RGB	  0x04	  /* bits 0 and 2 - RGB format */
#define	  COM7_YUV	  0x00	  /* YUV */
#define	  COM7_BAYER	  0x01	  /* Bayer format */
#define	  COM7_PBAYER	  0x05	  /* "Processed bayer" */
#define REG_COM8	0x13	/* Control 8 */
#define   COM8_FASTAEC	  0x80	  /* Enable fast AGC/AEC */
#define   COM8_AECSTEP	  0x40	  /* Unlimited AEC step size */
#define   COM8_BFILT	  0x20	  /* Band filter enable */
#define   COM8_AGC	  0x04	  /* Auto gain enable */
#define   COM8_AWB	  0x02	  /* White balance enable */
#define   COM8_AEC	  0x01	  /* Auto exposure enable */
#define REG_COM9	0x14	/* Control 9  - gain ceiling */
#define REG_COM10	0x15	/* Control 10 */
#define   COM10_HSYNC	  0x40	  /* HSYNC instead of HREF */
#define   COM10_PCLK_HB	  0x20	  /* Suppress PCLK on horiz blank */
#define   COM10_HREF_REV  0x08	  /* Reverse HREF */
#define   COM10_VS_LEAD	  0x04	  /* VSYNC on clock leading edge */
#define   COM10_VS_NEG	  0x02	  /* VSYNC negative */
#define   COM10_HS_NEG	  0x01	  /* HSYNC negative */
#define REG_HSTART	0x17	/* Horiz start high bits */
#define REG_HSTOP	0x18	/* Horiz stop high bits */
#define REG_VSTART	0x19	/* Vert start high bits */
#define REG_VSTOP	0x1a	/* Vert stop high bits */
#define REG_PSHFT	0x1b	/* Pixel delay after HREF */
#define REG_MIDH	0x1c	/* Manuf. ID high */
#define REG_MIDL	0x1d	/* Manuf. ID low */
#define REG_MVFP	0x1e	/* Mirror / vflip */
#define   MVFP_MIRROR	  0x20	  /* Mirror image */
#define   MVFP_FLIP	  0x10	  /* Vertical flip */

#define REG_AEW		0x24	/* AGC upper limit */
#define REG_AEB		0x25	/* AGC lower limit */
#define REG_VPT		0x26	/* AGC/AEC fast mode op region */
#define REG_HSYST	0x30	/* HSYNC rising edge delay */
#define REG_HSYEN	0x31	/* HSYNC falling edge delay */
#define REG_HREF	0x32	/* HREF pieces */
#define REG_TSLB	0x3a	/* lots of stuff */
#define   TSLB_YLAST	  0x04	  /* UYVY or VYUY - see com13 */
#define REG_COM11	0x3b	/* Control 11 */
#define   COM11_NIGHT	  0x80	  /* NIght mode enable */
#define   COM11_NMFR	  0x60	  /* Two bit NM frame rate */
#define   COM11_HZAUTO	  0x10	  /* Auto detect 50/60 Hz */
#define	  COM11_50HZ	  0x08	  /* Manual 50Hz select */
#define   COM11_EXP	  0x02
#define REG_COM12	0x3c	/* Control 12 */
#define   COM12_HREF	  0x80	  /* HREF always */
#define REG_COM13	0x3d	/* Control 13 */
#define   COM13_GAMMA	  0x80	  /* Gamma enable */
#define	  COM13_UVSAT	  0x40	  /* UV saturation auto adjustment */
#define   COM13_UVSWAP	  0x01	  /* V before U - w/TSLB */
#define REG_COM14	0x3e	/* Control 14 */
#define   COM14_DCWEN	  0x10	  /* DCW/PCLK-scale enable */
#define REG_EDGE	0x3f	/* Edge enhancement factor */
#define REG_COM15	0x40	/* Control 15 */
#define   COM15_R10F0	  0x00	  /* Data range 10 to F0 */
#define	  COM15_R01FE	  0x80	  /*            01 to FE */
#define   COM15_R00FF	  0xc0	  /*            00 to FF */
#define   COM15_RGB565	  0x10	  /* RGB565 output */
#define   COM15_RGB555	  0x30	  /* RGB555 output */
#define REG_COM16	0x41	/* Control 16 */
#define   COM16_AWBGAIN   0x08	  /* AWB gain enable */
#define REG_COM17	0x42	/* Control 17 */
#define   COM17_AECWIN	  0xc0	  /* AEC window - must match COM4 */
#define   COM17_CBAR	  0x08	  /* DSP Color bar */

#define REG_BRIGHT	0x55	/* Brightness */
#define REG_CONTRAS	0x56	/* Contrast control */

#define REG_GFIX	0x69	/* Fix gain control */

#define REG_RGB444	0x8c	/* RGB 444 control */
#define   R444_ENABLE	  0x02	  /* Turn on RGB444, overrides 5x5 */
#define   R444_RGBX	  0x01	  /* Empty nibble at end */

#define REG_HAECC1	0x9f	/* Hist AEC/AGC control 1 */
#define REG_HAECC2	0xa0	/* Hist AEC/AGC control 2 */

#define REG_BD50MAX	0xa5	/* 50hz banding step limit */
#define REG_HAECC3	0xa6	/* Hist AEC/AGC control 3 */
#define REG_HAECC4	0xa7	/* Hist AEC/AGC control 4 */
#define REG_HAECC5	0xa8	/* Hist AEC/AGC control 5 */
#define REG_HAECC6	0xa9	/* Hist AEC/AGC control 6 */
#define REG_HAECC7	0xaa	/* Hist AEC/AGC control 7 */
#define REG_BD60MAX	0xab	/* 60hz banding step limit */


/*
 * The default register settings, as obtained from OmniVision.  There
 * is really no making sense of most of these - lots of "reserved" values
 * and such.
 *
 * These settings give VGA YUYV.
 */

struct regval_list {
	unsigned char reg_num;
	unsigned char value;
};

static struct regval_list ov7670_default_regs[] = {
	{ REG_COM7, COM7_RESET },
/*
 * Clock scale: 3 = 15fps
 *              2 = 20fps
 *              1 = 30fps
 */
	{ REG_CLKRC, 0x1 },	/* OV: clock scale (15 fps) */
	{ REG_TSLB,  0x04 },	/* OV */
	{ REG_COM7, 0 },	/* VGA */
	/*
	 * Set the hardware window.  These values from OV don't entirely
	 * make sense - hstop is less than hstart.  But they work...
	 */
	{ REG_HSTART, 0x13 },	{ REG_HSTOP, 0x01 },
	{ REG_HREF, 0xb6 },	{ REG_VSTART, 0x02 },
	{ REG_VSTOP, 0x7a },	{ REG_VREF, 0x0a },

	{ REG_COM3, 0 },	{ REG_COM14, 0 },
	/* Mystery scaling numbers */
	{ 0x70, 0x3a },		{ 0x71, 0x35 },
	{ 0x72, 0x11 },		{ 0x73, 0xf0 },
	{ 0xa2, 0x02 },		{ REG_COM10, 0x0 },

	/* Gamma curve values */
	{ 0x7a, 0x20 },		{ 0x7b, 0x10 },
	{ 0x7c, 0x1e },		{ 0x7d, 0x35 },
	{ 0x7e, 0x5a },		{ 0x7f, 0x69 },
	{ 0x80, 0x76 },		{ 0x81, 0x80 },
	{ 0x82, 0x88 },		{ 0x83, 0x8f },
	{ 0x84, 0x96 },		{ 0x85, 0xa3 },
	{ 0x86, 0xaf },		{ 0x87, 0xc4 },
	{ 0x88, 0xd7 },		{ 0x89, 0xe8 },

	/* AGC and AEC parameters.  Note we start by disabling those features,
	   then turn them only after tweaking the values. */
	{ REG_COM8, COM8_FASTAEC | COM8_AECSTEP | COM8_BFILT },
	{ REG_GAIN, 0 },	{ REG_AECH, 0 },
	{ REG_COM4, 0x40 }, /* magic reserved bit */
	{ REG_COM9, 0x18 }, /* 4x gain + magic rsvd bit */
	{ REG_BD50MAX, 0x05 },	{ REG_BD60MAX, 0x07 },
	{ REG_AEW, 0x95 },	{ REG_AEB, 0x33 },
	{ REG_VPT, 0xe3 },	{ REG_HAECC1, 0x78 },
	{ REG_HAECC2, 0x68 },	{ 0xa1, 0x03 }, /* magic */
	{ REG_HAECC3, 0xd8 },	{ REG_HAECC4, 0xd8 },
	{ REG_HAECC5, 0xf0 },	{ REG_HAECC6, 0x90 },
	{ REG_HAECC7, 0x94 },
	{ REG_COM8, COM8_FASTAEC|COM8_AECSTEP|COM8_BFILT|COM8_AGC|COM8_AEC },

	/* Almost all of these are magic "reserved" values.  */
	{ REG_COM5, 0x61 },	{ REG_COM6, 0x4b },
	{ 0x16, 0x02 },		{ REG_MVFP, 0x07|MVFP_MIRROR },
	{ 0x21, 0x02 },		{ 0x22, 0x91 },
	{ 0x29, 0x07 },		{ 0x33, 0x0b },
	{ 0x35, 0x0b },		{ 0x37, 0x1d },
	{ 0x38, 0x71 },		{ 0x39, 0x2a },
	{ REG_COM12, 0x78 },	{ 0x4d, 0x40 },
	{ 0x4e, 0x20 },		{ REG_GFIX, 0 },
	{ 0x6b, 0x4a },		{ 0x74, 0x10 },
	{ 0x8d, 0x4f },		{ 0x8e, 0 },
	{ 0x8f, 0 },		{ 0x90, 0 },
	{ 0x91, 0 },		{ 0x96, 0 },
	{ 0x9a, 0 },		{ 0xb0, 0x84 },
	{ 0xb1, 0x0c },		{ 0xb2, 0x0e },
	{ 0xb3, 0x82 },		{ 0xb8, 0x0a },

	/* More reserved magic, some of which tweaks white balance */
	{ 0x43, 0x0a },		{ 0x44, 0xf0 },
	{ 0x45, 0x34 },		{ 0x46, 0x58 },
	{ 0x47, 0x28 },		{ 0x48, 0x3a },
	{ 0x59, 0x88 },		{ 0x5a, 0x88 },
	{ 0x5b, 0x44 },		{ 0x5c, 0x67 },
	{ 0x5d, 0x49 },		{ 0x5e, 0x0e },
	{ 0x6c, 0x0a },		{ 0x6d, 0x55 },
	{ 0x6e, 0x11 },		{ 0x6f, 0x9f }, /* "9e for advance AWB" */
	{ 0x6a, 0x40 },		{ REG_BLUE, 0x40 },
	{ REG_RED, 0x60 },
	{ REG_COM8, COM8_FASTAEC|COM8_AECSTEP|COM8_BFILT|COM8_AGC|COM8_AEC|COM8_AWB },

	/* Matrix coefficients */
	{ 0x4f, 0x80 },		{ 0x50, 0x80 },
	{ 0x51, 0 },		{ 0x52, 0x22 },
	{ 0x53, 0x5e },		{ 0x54, 0x80 },
	{ 0x58, 0x9e },

	{ REG_COM16, COM16_AWBGAIN },	{ REG_EDGE, 0 },
	{ 0x75, 0x05 },		{ 0x76, 0xe1 },
	{ 0x4c, 0 },		{ 0x77, 0x01 },
	{ REG_COM13, 0xc3 },	{ 0x4b, 0x09 },
	{ 0xc9, 0x60 },		{ REG_COM16, 0x38 },
	{ 0x56, 0x40 },

	{ 0x34, 0x11 },		{ REG_COM11, COM11_EXP },
	{ 0xa4, 0x88 },		{ 0x96, 0 },
	{ 0x97, 0x30 },		{ 0x98, 0x20 },
	{ 0x99, 0x30 },		{ 0x9a, 0x84 },
	{ 0x9b, 0x29 },		{ 0x9c, 0x03 },
	{ 0x9d, 0x4c },		{ 0x9e, 0x3f },
	{ 0x78, 0x04 },

	/* Extra-weird stuff.  Some sort of multiplexor register */
	{ 0x79, 0x01 },		{ 0xc8, 0xf0 },
	{ 0x79, 0x0f },		{ 0xc8, 0x00 },
	{ 0x79, 0x10 },		{ 0xc8, 0x7e },
	{ 0x79, 0x0a },		{ 0xc8, 0x80 },
	{ 0x79, 0x0b },		{ 0xc8, 0x01 },
	{ 0x79, 0x0c },		{ 0xc8, 0x0f },
	{ 0x79, 0x0d },		{ 0xc8, 0x20 },
	{ 0x79, 0x09 },		{ 0xc8, 0x80 },
	{ 0x79, 0x02 },		{ 0xc8, 0xc0 },
	{ 0x79, 0x03 },		{ 0xc8, 0x40 },
	{ 0x79, 0x05 },		{ 0xc8, 0x30 },
	{ 0x79, 0x26 },

	/* Not sure if these should be here */
	{ 0xf1, 0x10 },		{ 0x0f, 0x1d },
	{ 0x0f, 0x1f },

	{ 0xff, 0xff },	/* END MARKER */
};


/*
 * Here we'll try to encapsulate the changes for just the output
 * video format.
 *
 * RGB656 and YUV422 come from OV; RGB444 is homebrewed.
 *
 * IMPORTANT RULE: the first entry must be for COM7, see ov7670_s_fmt for why.
 */


static struct regval_list ov7670_fmt_yuv422[] = {
	{ REG_COM7, 0x0 },  /* Selects YUV mode */
	{ REG_RGB444, 0 },	/* No RGB444 please */
	{ REG_COM1, 0 },
	{ REG_COM15, COM15_R00FF },
	{ REG_COM9, 0x18 }, /* 4x gain ceiling; 0x8 is reserved bit */
	{ 0x4f, 0x80 }, 	/* "matrix coefficient 1" */
	{ 0x50, 0x80 }, 	/* "matrix coefficient 2" */
	{ 0x52, 0x22 }, 	/* "matrix coefficient 4" */
	{ 0x53, 0x5e }, 	/* "matrix coefficient 5" */
	{ 0x54, 0x80 }, 	/* "matrix coefficient 6" */
	{ REG_COM13, COM13_GAMMA|COM13_UVSAT },
	{ 0xff, 0xff },
};

static struct regval_list ov7670_fmt_rgb565[] = {
	{ REG_COM7, COM7_RGB },	/* Selects RGB mode */
	{ REG_RGB444, 0 },	/* No RGB444 please */
	{ REG_COM1, 0x0 },
	{ REG_COM15, COM15_RGB565 },
	{ REG_COM9, 0x38 }, 	/* 16x gain ceiling; 0x8 is reserved bit */
	{ 0x4f, 0xb3 }, 	/* "matrix coefficient 1" */
	{ 0x50, 0xb3 }, 	/* "matrix coefficient 2" */
	{ 0x52, 0x3d }, 	/* "matrix coefficient 4" */
	{ 0x53, 0xa7 }, 	/* "matrix coefficient 5" */
	{ 0x54, 0xe4 }, 	/* "matrix coefficient 6" */
	{ REG_COM13, COM13_GAMMA|COM13_UVSAT },
	{ 0xff, 0xff },
};

static struct regval_list ov7670_fmt_rgb444[] = {
	{ REG_COM7, COM7_RGB },	/* Selects RGB mode */
	{ REG_RGB444, R444_ENABLE },	/* Enable xxxxrrrr ggggbbbb */
	{ REG_COM1, 0x40 },	/* Magic reserved bit */
	{ REG_COM15, COM15_R01FE|COM15_RGB565 }, /* Data range needed? */
	{ REG_COM9, 0x38 }, 	/* 16x gain ceiling; 0x8 is reserved bit */
	{ 0x4f, 0xb3 }, 	/* "matrix coefficient 1" */
	{ 0x50, 0xb3 }, 	/* "matrix coefficient 2" */
	{ 0x52, 0x3d }, 	/* "matrix coefficient 4" */
	{ 0x53, 0xa7 }, 	/* "matrix coefficient 5" */
	{ 0x54, 0xe4 }, 	/* "matrix coefficient 6" */
	{ REG_COM13, COM13_GAMMA|COM13_UVSAT|0x2 },  /* Magic rsvd bit */
	{ 0xff, 0xff },
};




/*
 * Low-level register I/O.
 */

static int ov7670_read(struct i2c_client *c, unsigned char reg,
		unsigned char *value)
{
	int ret;

	ret = i2c_smbus_read_byte_data(c, reg);
	if (ret > 0)
		*value = (unsigned char) ret;
	return ret;
}


static int ov7670_write(struct i2c_client *c, unsigned char reg,
		unsigned char value)
{
	return i2c_smbus_write_byte_data(c, reg, value);
}


/*
 * Write a list of register settings; ff/ff stops the process.
 */
static int ov7670_write_array(struct i2c_client *c, struct regval_list *vals)
{
	while (vals->reg_num != 0xff || vals->value != 0xff) {
		int ret = ov7670_write(c, vals->reg_num, vals->value);
		if (ret < 0)
			return ret;
		vals++;
	}
	return 0;
}


/*
 * Stuff that knows about the sensor.
 */
static void ov7670_reset(struct i2c_client *client)
{
	ov7670_write(client, REG_COM7, COM7_RESET);
	msleep(1);
}


static int ov7670_init(struct i2c_client *client)
{
	return ov7670_write_array(client, ov7670_default_regs);
}



static int ov7670_detect(struct i2c_client *client)
{
	unsigned char v;
	int ret;

	ret = ov7670_init(client);
	if (ret < 0)
		return ret;
	ret = ov7670_read(client, REG_MIDH, &v);
	if (ret < 0)
		return ret;
	if (v != 0x7f) /* OV manuf. id. */
		return -ENODEV;
	ret = ov7670_read(client, REG_MIDL, &v);
	if (ret < 0)
		return ret;
	if (v != 0xa2)
		return -ENODEV;
	/*
	 * OK, we know we have an OmniVision chip...but which one?
	 */
	ret = ov7670_read(client, REG_PID, &v);
	if (ret < 0)
		return ret;
	if (v != 0x76)  /* PID + VER = 0x76 / 0x73 */
		return -ENODEV;
	ret = ov7670_read(client, REG_VER, &v);
	if (ret < 0)
		return ret;
	if (v != 0x73)  /* PID + VER = 0x76 / 0x73 */
		return -ENODEV;
	return 0;
}





static struct ov7670_format_struct {
	__u8 *desc;
	__u32 pixelformat;
	struct regval_list *regs;
} ov7670_formats[] = {
	{
		.desc		= "YUYV 4:2:2",
		.pixelformat	= V4L2_PIX_FMT_YUYV,
		.regs 		= ov7670_fmt_yuv422,
	},
	{
		.desc		= "RGB 444",
		.pixelformat	= V4L2_PIX_FMT_RGB444,
		.regs		= ov7670_fmt_rgb444,
	},
	{
		.desc		= "RGB 565",
		.pixelformat	= V4L2_PIX_FMT_RGB565,
		.regs		= ov7670_fmt_rgb565,
	},
	/*
	 * Pretend we do RGB32.  This is here on the assumption that the
	 * upper layer will reformat RGB444 appropriately.
	 *
	 * The entire purpose for this thing's existence is to enable easy
	 * display of RGB444 for debugging purposes.  It will come out soon.
	 */
	{
		.desc		= "RGB32 (faked)",
		.pixelformat	= V4L2_PIX_FMT_RGB32,
		.regs		= ov7670_fmt_rgb444,
	},
};
#define N_OV7670_FMTS (sizeof(ov7670_formats)/sizeof(ov7670_formats[0]))

/*
 * All formats we support are 2 bytes/pixel.
 */
#define BYTES_PER_PIXEL 2

/*
 * Then there is the issue of window sizes.  Try to capture the info here.
 */
static struct ov7670_win_size {
	int	width;
	int	height;
	unsigned char com7_bit;
	int	hstart;		/* Start/stop values for the camera.  Note */
	int	hstop;		/* that they do not always make complete */
	int	vstart;		/* sense to humans, but evidently the sensor */
	int	vstop;		/* will do the right thing... */
/* h/vref stuff */
} ov7670_win_sizes[] = {
	/* VGA */
	{
		.width		= VGA_WIDTH,
		.height		= VGA_HEIGHT,
		.com7_bit	= COM7_FMT_VGA,
		.hstart		= 158,		/* These values from */
		.hstop		=  14,		/* Omnivision */
		.vstart		=  10,
		.vstop		= 490,
	},
	/* CIF */
	{
		.width		= CIF_WIDTH,
		.height		= CIF_HEIGHT,
		.com7_bit	= COM7_FMT_CIF,
		.hstart		= 170,		/* Empirically determined */
		.hstop		=  90,
		.vstart		=  14,
		.vstop		= 494,
	},
	/* QVGA */
	{
		.width		= QVGA_WIDTH,
		.height		= QVGA_HEIGHT,
		.com7_bit	= COM7_FMT_QVGA,
		.hstart		= 164,		/* Empirically determined */
		.hstop		=  20,
		.vstart		=  14,
		.vstop		= 494,
	},
};

#define N_WIN_SIZES (sizeof(ov7670_win_sizes)/sizeof(ov7670_win_sizes[0]))


/*
 * Store a set of start/stop values into the camera.
 */
static int ov7670_set_hw(struct i2c_client *client, int hstart, int hstop,
		int vstart, int vstop)
{
	int ret;
	unsigned char v;
/*
 * Horizontal: 11 bits, top 8 live in hstart and hstop.  Bottom 3 of
 * hstart are in href[2:0], bottom 3 of hstop in href[5:3].  There is
 * a mystery "edge offset" value in the top two bits of href.
 */
	ret =  ov7670_write(client, REG_HSTART, (hstart >> 3) & 0xff);
	ret += ov7670_write(client, REG_HSTOP, (hstop >> 3) & 0xff);
	ret += ov7670_read(client, REG_HREF, &v);
	v = (v & 0xc0) | ((hstop & 0x7) << 3) | (hstart & 0x7);
	msleep(10);
	ret += ov7670_write(client, REG_HREF, v);
/*
 * Vertical: similar arrangement, but only 10 bits.
 */
	ret += ov7670_write(client, REG_VSTART, (vstart >> 2) & 0xff);
	ret += ov7670_write(client, REG_VSTOP, (vstop >> 2) & 0xff);
	ret += ov7670_read(client, REG_VREF, &v);
	v = (v & 0xf0) | ((vstop & 0x3) << 2) | (vstart & 0x3);
	msleep(10);
	ret += ov7670_write(client, REG_VREF, v);
	return ret;
}


static int ov7670_enum_fmt(struct i2c_client *c, struct v4l2_fmtdesc *fmt)
{
	struct ov7670_format_struct *ofmt;

	if (fmt->index >= N_OV7670_FMTS)
		return -EINVAL;

	ofmt = ov7670_formats + fmt->index;
	fmt->flags = 0;
	strcpy(fmt->description, ofmt->desc);
	fmt->pixelformat = ofmt->pixelformat;
	return 0;
}


static int ov7670_try_fmt(struct i2c_client *c, struct v4l2_format *fmt,
		struct ov7670_format_struct **ret_fmt,
		struct ov7670_win_size **ret_wsize)
{
	int index;
	struct ov7670_win_size *wsize;
	struct v4l2_pix_format *pix = &fmt->fmt.pix;

	for (index = 0; index < N_OV7670_FMTS; index++)
		if (ov7670_formats[index].pixelformat == pix->pixelformat)
			break;
	if (index >= N_OV7670_FMTS)
		return -EINVAL;
	if (ret_fmt != NULL)
		*ret_fmt = ov7670_formats + index;
	/*
	 * Fields: the OV devices claim to be progressive.
	 */
	if (pix->field == V4L2_FIELD_ANY)
		pix->field = V4L2_FIELD_NONE;
	else if (pix->field != V4L2_FIELD_NONE)
		return -EINVAL;
	/*
	 * Round requested image size down to the nearest
	 * we support, but not below the smallest.
	 */
	for (wsize = ov7670_win_sizes; wsize < ov7670_win_sizes + N_WIN_SIZES;
	     wsize++)
		if (pix->width >= wsize->width && pix->height >= wsize->height)
			break;
	if (wsize > ov7670_win_sizes + N_WIN_SIZES)
		wsize--;   /* Take the smallest one */
	if (ret_wsize != NULL)
		*ret_wsize = wsize;
	/*
	 * Note the size we'll actually handle.
	 */
	pix->width = wsize->width;
	pix->height = wsize->height;
	pix->bytesperline = pix->width*BYTES_PER_PIXEL;
	if (pix->pixelformat == V4L2_PIX_FMT_RGB32)
		pix->bytesperline *= 2;
	pix->sizeimage = pix->height*pix->bytesperline;
	return 0;

}

/*
 * Set a format.
 */
static int ov7670_s_fmt(struct i2c_client *c, struct v4l2_format *fmt)
{
	int ret;
	struct ov7670_format_struct *ovfmt;
	struct ov7670_win_size *wsize;
	unsigned char com7;

	ret = ov7670_try_fmt(c, fmt, &ovfmt, &wsize);
	if (ret)
		return ret;
	/*
	 * COM7 is a pain in the ass, it doesn't like to be read then
	 * quickly written afterward.  But we have everything we need
	 * to set it absolutely here, as long as the format-specific
	 * register sets list it first.
	 */
	com7 = ovfmt->regs[0].value;
	com7 |= wsize->com7_bit;
	ov7670_write(c, REG_COM7, com7);
	/*
	 * Now write the rest of the array.  Also store start/stops
	 */
	ov7670_write_array(c, ovfmt->regs + 1);
	ov7670_set_hw(c, wsize->hstart, wsize->hstop, wsize->vstart,
			wsize->vstop);
	return 0;
}

/*
 * Code for dealing with controls.
 */

/*
 * Some weird registers seem to store values in a sign/magnitude format!
 */
static unsigned char ov7670_sm_to_abs(unsigned char v)
{
	if ((v & 0x80) == 0)
		return v + 128;
	else
		return 128 - (v & 0x7f);
}


static unsigned char ov7670_abs_to_sm(unsigned char v)
{
	if (v > 127)
		return v & 0x7f;
	else
		return (128 - v) | 0x80;
}

static int ov7670_t_brightness(struct i2c_client *client, unsigned char value)
{
	unsigned char com8;
	int ret;

	ov7670_read(client, REG_COM8, &com8);
	com8 &= ~COM8_AEC;
	ov7670_write(client, REG_COM8, com8);
	value = ov7670_abs_to_sm(value);
	ret = ov7670_write(client, REG_BRIGHT, value);
	return ret;
}

static int ov7670_q_brightness(struct i2c_client *client, unsigned char *value)
{
	int ret;
	ret = ov7670_read(client, REG_BRIGHT, value);
	*value = ov7670_sm_to_abs(*value);
	return ret;
}

static int ov7670_t_contrast(struct i2c_client *client, unsigned char value)
{
	return ov7670_write(client, REG_CONTRAS, value);
}

static int ov7670_q_contrast(struct i2c_client *client, unsigned char *value)
{
	return ov7670_read(client, REG_CONTRAS, value);
}

static int ov7670_q_hflip(struct i2c_client *client, unsigned char *value)
{
	int ret;
	unsigned char v;

	ret = ov7670_read(client, REG_MVFP, &v);
	*value = (v & MVFP_MIRROR) == MVFP_MIRROR;
	return ret;
}


static int ov7670_t_hflip(struct i2c_client *client, unsigned char value)
{
	unsigned char v;
	int ret;

	ret = ov7670_read(client, REG_MVFP, &v);
	if (value)
		v |= MVFP_MIRROR;
	else
		v &= ~MVFP_MIRROR;
	msleep(10);  /* FIXME */
	ret += ov7670_write(client, REG_MVFP, v);
	return ret;
}



static int ov7670_q_vflip(struct i2c_client *client, unsigned char *value)
{
	int ret;
	unsigned char v;

	ret = ov7670_read(client, REG_MVFP, &v);
	*value = (v & MVFP_FLIP) == MVFP_FLIP;
	return ret;
}


static int ov7670_t_vflip(struct i2c_client *client, unsigned char value)
{
	unsigned char v;
	int ret;

	ret = ov7670_read(client, REG_MVFP, &v);
	if (value)
		v |= MVFP_FLIP;
	else
		v &= ~MVFP_FLIP;
	msleep(10);  /* FIXME */
	ret += ov7670_write(client, REG_MVFP, v);
	return ret;
}


static struct ov7670_control {
	struct v4l2_queryctrl qc;
	int (*query)(struct i2c_client *c, unsigned char *value);
	int (*tweak)(struct i2c_client *c, unsigned char value);
} ov7670_controls[] =
{
	{
		.qc = {
			.id = V4L2_CID_BRIGHTNESS,
			.type = V4L2_CTRL_TYPE_INTEGER,
			.name = "Brightness",
			.minimum = 0,
			.maximum = 255,
			.step = 1,
			.default_value = 0x80,
			.flags = V4L2_CTRL_FLAG_SLIDER
		},
		.tweak = ov7670_t_brightness,
		.query = ov7670_q_brightness,
	},
	{
		.qc = {
			.id = V4L2_CID_CONTRAST,
			.type = V4L2_CTRL_TYPE_INTEGER,
			.name = "Contrast",
			.minimum = 0,
			.maximum = 127,
			.step = 1,
			.default_value = 0x40,   /* XXX ov7670 spec */
			.flags = V4L2_CTRL_FLAG_SLIDER
		},
		.tweak = ov7670_t_contrast,
		.query = ov7670_q_contrast,
	},
	{
		.qc = {
			.id = V4L2_CID_VFLIP,
			.type = V4L2_CTRL_TYPE_BOOLEAN,
			.name = "Vertical flip",
			.minimum = 0,
			.maximum = 1,
			.step = 1,
			.default_value = 0,
		},
		.tweak = ov7670_t_vflip,
		.query = ov7670_q_vflip,
	},
	{
		.qc = {
			.id = V4L2_CID_HFLIP,
			.type = V4L2_CTRL_TYPE_BOOLEAN,
			.name = "Horizontal mirror",
			.minimum = 0,
			.maximum = 1,
			.step = 1,
			.default_value = 0,
		},
		.tweak = ov7670_t_hflip,
		.query = ov7670_q_hflip,
	},
};
#define N_CONTROLS (sizeof(ov7670_controls)/sizeof(ov7670_controls[0]))

static struct ov7670_control *ov7670_find_control(__u32 id)
{
	int i;

	for (i = 0; i < N_CONTROLS; i++)
		if (ov7670_controls[i].qc.id == id)
			return ov7670_controls + i;
	return NULL;
}


static int ov7670_queryctrl(struct i2c_client *client,
		struct v4l2_queryctrl *qc)
{
	struct ov7670_control *ctrl = ov7670_find_control(qc->id);

	if (ctrl == NULL)
		return -EINVAL;
	*qc = ctrl->qc;
	return 0;
}

static int ov7670_g_ctrl(struct i2c_client *client, struct v4l2_control *ctrl)
{
	struct ov7670_control *octrl = ov7670_find_control(ctrl->id);
	int ret;
	unsigned char v;

	if (octrl == NULL)
		return -EINVAL;
	ret = octrl->query(client, &v);
	if (ret >= 0) {
		ctrl->value = v;
		return 0;
	}
	return ret;
}

static int ov7670_s_ctrl(struct i2c_client *client, struct v4l2_control *ctrl)
{
	struct ov7670_control *octrl = ov7670_find_control(ctrl->id);

	if (octrl == NULL)
		return -EINVAL;
	return octrl->tweak(client, ctrl->value);
}







/*
 * Basic i2c stuff.
 */
static struct i2c_driver ov7670_driver;

static int ov7670_attach(struct i2c_adapter *adapter)
{
	int ret;
	struct i2c_client *client;

	printk(KERN_ERR "ov7670 attach, id = %d\n", adapter->id);
	/*
	 * For now: only deal with adapters we recognize.
	 */
	if (adapter->id != I2C_HW_SMBUS_CAFE)
		return -ENODEV;

	printk(KERN_ERR "ov7670 accepting\n");
	client = kzalloc(sizeof (struct i2c_client), GFP_KERNEL);
	if (! client)
		return -ENOMEM;
	client->adapter = adapter;
	client->addr = OV7670_I2C_ADDR;
	client->driver = &ov7670_driver,
	strcpy(client->name, "OV7670");
	/* Do we need clientdata? */

	/*
	 * Make sure it's an ov7670
	 */
	ret = ov7670_detect(client);
	printk(KERN_ERR "detect result is %d\n", ret);
	if (ret)
		goto out_free;
	i2c_attach_client(client);
	return 0;

  out_free:
	kfree(client);
	return ret;
}


static int ov7670_detach(struct i2c_client *client)
{
	i2c_detach_client(client);
	kfree(client);
	return 0;
}


static int ov7670_command(struct i2c_client *client, unsigned int cmd,
		void *arg)
{
	switch (cmd) {
	case VIDIOC_INT_G_CHIP_IDENT:
		* (enum v4l2_chip_ident *) arg = V4L2_IDENT_OV7670;
		return 0;

	case VIDIOC_INT_RESET:
		ov7670_reset(client);
		return 0;

	case VIDIOC_INT_INIT:
		return ov7670_init(client);

	case VIDIOC_ENUM_FMT:
		return ov7670_enum_fmt(client, (struct v4l2_fmtdesc *) arg);
	case VIDIOC_TRY_FMT:
		return ov7670_try_fmt(client, (struct v4l2_format *) arg, NULL, NULL);
	case VIDIOC_S_FMT:
		return ov7670_s_fmt(client, (struct v4l2_format *) arg);
	case VIDIOC_QUERYCTRL:
		return ov7670_queryctrl(client, (struct v4l2_queryctrl *) arg);
	case VIDIOC_S_CTRL:
		return ov7670_s_ctrl(client, (struct v4l2_control *) arg);
	case VIDIOC_G_CTRL:
		return ov7670_g_ctrl(client, (struct v4l2_control *) arg);
	/* Todo:
	   g/s_parm
	   initialization
	*/
	}
	return -EINVAL;
}



static struct i2c_driver ov7670_driver = {
	.driver = {
		.name = "ov7670",
	},
	.id 		= I2C_DRIVERID_OV7670,
	.class 		= I2C_CLASS_CAM_DIGITAL,
	.attach_adapter = ov7670_attach,
	.detach_client	= ov7670_detach,
	.command	= ov7670_command,
};


/*
 * Module initialization
 */
static int __init ov7670_mod_init(void)
{
	printk(KERN_NOTICE "OmniVision ov7670 sensor driver, at your service\n");
	return i2c_add_driver(&ov7670_driver);
}

static void __exit ov7670_mod_exit(void)
{
	i2c_del_driver(&ov7670_driver);
}

module_init(ov7670_mod_init);
module_exit(ov7670_mod_exit);