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authorFrank Schaefer <fschaefer.oss@googlemail.com>2013-03-10 07:25:25 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2013-03-18 20:18:29 -0300
commit7f6301d1257505d35e87ef1cb8eeee268e63a123 (patch)
tree17fa90a1374d48dc32adf6eaf3aec7633886eac1
parent195281d0dc6a2fc1824d5da9abd2924bce0fa698 (diff)
downloadlinaro-lsk-7f6301d1257505d35e87ef1cb8eeee268e63a123.tar.gz
[media] em28xx-i2c: relax error check in em28xx_i2c_recv_bytes()
It turned out that some devices return less bytes then requested via i2c when ALL of the following 3 conditions are met: - i2c bus B is used - there was no attempt to write to the specified slave address before - no device present at the specified slave address With the current code, this triggers an -EIO error and prints a message to the system log. Because it can happen very often during device probing, it is better to ignore this error and bail out silently after the follwing i2c transaction success check with -ENODEV. [mchehab@redhat.com: a small CodingStyle fix] Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
-rw-r--r--drivers/media/usb/em28xx/em28xx-i2c.c22
1 files changed, 11 insertions, 11 deletions
diff --git a/drivers/media/usb/em28xx/em28xx-i2c.c b/drivers/media/usb/em28xx/em28xx-i2c.c
index d4a48cb1202..de9b2086ab2 100644
--- a/drivers/media/usb/em28xx/em28xx-i2c.c
+++ b/drivers/media/usb/em28xx/em28xx-i2c.c
@@ -227,18 +227,18 @@ static int em28xx_i2c_recv_bytes(struct em28xx *dev, u16 addr, u8 *buf, u16 len)
/* Read data from i2c device */
ret = dev->em28xx_read_reg_req_len(dev, 2, addr, buf, len);
- if (ret != len) {
- if (ret < 0) {
- em28xx_warn("reading from i2c device at 0x%x failed "
- "(error=%i)\n", addr, ret);
- return ret;
- } else {
- em28xx_warn("%i bytes requested from i2c device at "
- "0x%x, but %i bytes received\n",
- len, addr, ret);
- return -EIO;
- }
+ 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 of the i2c operation */
ret = dev->em28xx_read_reg(dev, 0x05);