From 7f6301d1257505d35e87ef1cb8eeee268e63a123 Mon Sep 17 00:00:00 2001 From: Frank Schaefer Date: Sun, 10 Mar 2013 07:25:25 -0300 Subject: [PATCH] [media] em28xx-i2c: relax error check in em28xx_i2c_recv_bytes() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Mauro Carvalho Chehab --- drivers/media/usb/em28xx/em28xx-i2c.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/drivers/media/usb/em28xx/em28xx-i2c.c b/drivers/media/usb/em28xx/em28xx-i2c.c index d4a48cb1202e..de9b2086ab2d 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); -- 2.20.1