Em Sat, 23 Mar 2013 18:27:08 +0100
Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx> escreveu:
> The webcam "SpeedLink VAD Laplace" (em2765 + ov2640) uses a special algorithm
> for i2c communication with the sensor, which is connected to a second i2c bus.
>
> We don't know yet how to find out which devices support/use it.
> It's very likely used by all em25xx and em276x+ bridges.
> Tests with other em28xx chips (em2820, em2882/em2883) show, that this
> algorithm always succeeds there although no slave device is connected.
>
> The algorithm likely also works for real i2c client devices (OV2640 uses SCCB),
> because the Windows driver seems to use it for probing Samsung and Kodak
> sensors.
>
> Signed-off-by: Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx>
> ---
> drivers/media/usb/em28xx/em28xx-cards.c | 8 +-
> drivers/media/usb/em28xx/em28xx-i2c.c | 229 +++++++++++++++++++++++++------
> drivers/media/usb/em28xx/em28xx.h | 10 +-
> 3 Dateien geändert, 205 Zeilen hinzugefügt(+), 42 Zeilen entfernt(-)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index cb7cdd3..033b6cb 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -3139,15 +3139,19 @@ static int em28xx_init_dev(struct em28xx *dev, struct usb_device *udev,
> rt_mutex_init(&dev->i2c_bus_lock);
>
> /* register i2c bus 0 */
> - retval = em28xx_i2c_register(dev, 0);
> + if (dev->board.is_em2800)
> + retval = em28xx_i2c_register(dev, 0, EM28XX_I2C_ALGO_EM2800);
> + else
> + retval = em28xx_i2c_register(dev, 0, EM28XX_I2C_ALGO_EM28XX);
> if (retval < 0) {
> em28xx_errdev("%s: em28xx_i2c_register bus 0 - error [%d]!\n",
> __func__, retval);
> goto unregister_dev;
> }
>
> + /* register i2c bus 1 */
> if (dev->def_i2c_bus) {
> - retval = em28xx_i2c_register(dev, 1);
> + retval = em28xx_i2c_register(dev, 1, EM28XX_I2C_ALGO_EM28XX);
> if (retval < 0) {
> em28xx_errdev("%s: em28xx_i2c_register bus 1 - error [%d]!\n",
> __func__, retval);
> diff --git a/drivers/media/usb/em28xx/em28xx-i2c.c b/drivers/media/usb/em28xx/em28xx-i2c.c
> index 9e2fa41..ab14ac3 100644
> --- a/drivers/media/usb/em28xx/em28xx-i2c.c
> +++ b/drivers/media/usb/em28xx/em28xx-i2c.c
> @@ -5,6 +5,7 @@
> Markus Rechberger <mrechberger@xxxxxxxxx>
> Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxx>
> Sascha Sommer <saschasommer@xxxxxxxxxx>
> + Copyright (C) 2013 Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx>
>
> This program is free software; you can redistribute it and/or modify
> it under the terms of the GNU General Public License as published by
> @@ -274,6 +275,176 @@ static int em28xx_i2c_check_for_device(struct em28xx *dev, u16 addr)
> }
>
> /*
> + * em25xx_bus_B_send_bytes
> + * write bytes to the i2c device
> + */
> +static int em25xx_bus_B_send_bytes(struct em28xx *dev, u16 addr, u8 *buf,
> + u16 len)
> +{
> + int ret;
> +
> + if (len < 1 || len > 64)
> + return -EOPNOTSUPP;
> + /* NOTE: limited by the USB ctrl message constraints
> + * Zero length reads always succeed, even if no device is connected */
> +
> + /* Set register and write value */
> + ret = dev->em28xx_write_regs_req(dev, 0x06, addr, buf, len);
> + /* NOTE:
> + * 0 byte writes always succeed, even if no device is connected. */
You already noticed it on the previous note.
> + if (ret != len) {
> + if (ret < 0) {
> + em28xx_warn("writing to i2c device at 0x%x failed "
> + "(error=%i)\n", addr, ret);
> + return ret;
> + } else {
> + em28xx_warn("%i bytes write to i2c device at 0x%x "
> + "requested, but %i bytes written\n",
> + len, addr, ret);
> + return -EIO;
> + }
> + }
> + /* Check success */
> + ret = dev->em28xx_read_reg_req(dev, 0x08, 0x0000);
> + /* NOTE: the only error we've seen so far is
> + * 0x01 when the slave device is not present */
> + if (ret == 0x00) {
Please simplify. just use:
if (!ret)
> + return len;
> + } else if (ret > 0) {
> + return -ENODEV;
> + }
> +
> + return ret;
> + /* NOTE: With chips which do not support this operation,
> + * it seems to succeed ALWAYS ! (even if no device connected) */
Sorry, but I didn't get what you're trying to explain here. What are those
em25xx chips that don't support this operation?
> +}
> +
> +/*
> + * em25xx_bus_B_recv_bytes
> + * read bytes from the i2c device
> + */
> +static int em25xx_bus_B_recv_bytes(struct em28xx *dev, u16 addr, u8 *buf,
> + u16 len)
> +{
> + int ret;
> +
> + if (len < 1 || len > 64)
> + return -EOPNOTSUPP;
> + /* NOTE: limited by the USB ctrl message constraints
> + * Zero length reads always succeed, even if no device is connected */
You already explained about the zero length before.
> +
> + /* Read value */
> + ret = dev->em28xx_read_reg_req_len(dev, 0x06, addr, buf, len);
> + /* NOTE:
> + * 0 byte reads always succeed, even if no device is connected. */
You're insistent on that, won't you? ;)
> + if (ret < 0) {
> + em28xx_warn("reading from i2c device at 0x%x failed (error=%i)\n",
> + addr, ret);
> + return ret;
> + }
> + /* NOTE: some devices with two i2c busses have the bad habit to return 0
> + * bytes if we are on bus B AND there was no write attempt to the
> + * specified slave address before AND no device is present at the
> + * requested slave address.
> + * Anyway, the next check will fail with -ENODEV in this case, so avoid
> + * spamming the system log on device probing and do nothing here.
> + */
> +
> + /* Check success */
> + ret = dev->em28xx_read_reg_req(dev, 0x08, 0x0000);
> + /* NOTE: the only error we've seen so far is
> + * 0x01 when the slave device is not present */
> + if (ret == 0x00) {
Same as already noticed.
> + return len;
> + } else if (ret > 0) {
> + return -ENODEV;
> + }
> +
> + return ret;
> + /* NOTE: With chips which do not support this operation,
> + * it seems to succeed ALWAYS ! (even if no device connected) */
Again, didn't understand what you're meaning.
Regards,
Mauro
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
