Am 22.03.2017 um 15:46 schrieb Mauro Carvalho Chehab:
Em Sun, 19 Feb 2017 19:29:18 +0100 Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx> escreveu:Use i2c_smbus_read_word_data() instead of i2c_master_send() and i2c_master_recv() for reading the ID of Micorn sensors. Bytes need to be swapped afterwards, because i2c_smbus_read_word_data() assumes that the received bytes are little-endian byte order (as specified by smbus), while Micron sensors with 16 bit register width use big endian byte order. Signed-off-by: Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx> --- drivers/media/usb/em28xx/em28xx-camera.c | 28 ++++------------------------ 1 file changed, 4 insertions(+), 24 deletions(-) diff --git a/drivers/media/usb/em28xx/em28xx-camera.c b/drivers/media/usb/em28xx/em28xx-camera.c index 7b4129ab1cf9..4839479624e7 100644 --- a/drivers/media/usb/em28xx/em28xx-camera.c +++ b/drivers/media/usb/em28xx/em28xx-camera.c @@ -106,8 +106,6 @@ static int em28xx_probe_sensor_micron(struct em28xx *dev) { int ret, i; char *name; - u8 reg; - __be16 id_be; u16 id;struct i2c_client *client = &dev->i2c_client[dev->def_i2c_bus];@@ -115,10 +113,8 @@ static int em28xx_probe_sensor_micron(struct em28xx *dev) dev->em28xx_sensor = EM28XX_NOSENSOR; for (i = 0; micron_sensor_addrs[i] != I2C_CLIENT_END; i++) { client->addr = micron_sensor_addrs[i]; - /* NOTE: i2c_smbus_read_word_data() doesn't work with BE data */ /* Read chip ID from register 0x00 */ - reg = 0x00; - ret = i2c_master_send(client, ®, 1); + ret = i2c_smbus_read_word_data(client, 0x00); /* assumes LE */ if (ret < 0) { if (ret != -ENXIO) dev_err(&dev->intf->dev, @@ -126,24 +122,9 @@ static int em28xx_probe_sensor_micron(struct em28xx *dev) client->addr << 1, ret); continue; } - ret = i2c_master_recv(client, (u8 *)&id_be, 2); - if (ret < 0) { - dev_err(&dev->intf->dev, - "couldn't read from i2c device 0x%02x: error %i\n", - client->addr << 1, ret); - continue; - } - id = be16_to_cpu(id_be); + id = swab16(ret); /* LE -> BE */That's wrong! You can't assume that CPU is BE, as some archs use LE. You should, instead, call le16_to_cpu(), to be sure that it will be doing the right thing. Something like: id = le16_to_cpu((__le16)ret);
SMBus read/write word transfers are always LE (see SMBus spec section 6.5.5),
which is also what i2c_smbus_xfer_emulated() assumes: http://lxr.free-electrons.com/source/drivers/i2c/i2c-core.c#L3485 Regards, Frank
Regards, Thanks, Mauro
