[media] em28xx: consider the message length limitation of the i2c adapter when readin...

EEPROMs are currently read in blocks of 16 bytes, but the em2800 is limited
to 4 bytes per read. All other chip variants support reading of max. 64 bytes
at once (according to the em258x datasheet; also verified with em2710, em2882,
and em28174).
Since em2800_i2c_recv_bytes() has been fixed to return with -EOPNOTSUPP when
more than 4 bytes are requested, EEPROM reading with this chip is broken.
It was actually broken before that change, too, it just didn't throw an error
because the i2c adapter silently returned trash data (for all reads >1 byte !).

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/media/usb/em28xx/em28xx-i2c.c b/drivers/media/usb/em28xx/em28xx-i2c.c
index f784b516ae1cf5180f7f20affafc0979e37ebc07..9ae8f6051d8ebf280ced3d77080402829ae04f6e 100644 (file)
--- a/drivers/media/usb/em28xx/em28xx-i2c.c
+++ b/drivers/media/usb/em28xx/em28xx-i2c.c
@@ -379,7 +379,7 @@ static int em28xx_i2c_eeprom(struct em28xx *dev, unsigned char *eedata, int len)
 {
        unsigned char buf, *p = eedata;
        struct em28xx_eeprom *em_eeprom = (void *)eedata;
-       int i, err, size = len, block;
+       int i, err, size = len, block, block_max;
 
        if (dev->chip_id == CHIP_ID_EM2874 ||
            dev->chip_id == CHIP_ID_EM28174 ||
@@ -412,9 +412,15 @@ static int em28xx_i2c_eeprom(struct em28xx *dev, unsigned char *eedata, int len)
                       dev->name, err);
                return err;
        }
+
+       if (dev->board.is_em2800)
+               block_max = 4;
+       else
+               block_max = 64;
+
        while (size > 0) {
-               if (size > 16)
-                       block = 16;
+               if (size > block_max)
+                       block = block_max;
                else
                        block = size;