Hi Chris,
On Tue, Jul 11, 2017 at 6:29 PM, Chris Brandt <chris.brandt@xxxxxxxxxxx> wrote:
> The existing code gives an incorrect value.
> The buffer pointer 'buf' was of type unsigned short *, and 'count' was a
> number in bytes, so the pointer should have been cast before doing any
> pointer arithmetic.
>
> Since we know the code before it is doing as many 4-byte transfers as
> possible, we just need a pointer to where it left off in the buffer, hence
> zeroing out the bottom 2 bits of count for out math.
s/out/our/
> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Fixes: 8185e51f358a: ("mmc: tmio-mmc: add support for 32bit data port")
> Signed-off-by: Chris Brandt <chris.brandt@xxxxxxxxxxx>
> ---
> drivers/mmc/host/tmio_mmc_core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/tmio_mmc_core.c b/drivers/mmc/host/tmio_mmc_core.c
> index 77e7b56a9099..5dfc556ccedf 100644
> --- a/drivers/mmc/host/tmio_mmc_core.c
> +++ b/drivers/mmc/host/tmio_mmc_core.c
> @@ -428,7 +428,7 @@ static void tmio_mmc_transfer_data(struct tmio_mmc_host *host,
> if (!(count & 0x3))
> return;
>
> - buf8 = (u8 *)(buf + (count >> 2));
> + buf8 = (u8 *)buf + (count & ~3);
> count %= 4;
While correct, this is IMHO still difficult to understand for the casual reader.
Given the code before casts to "u32 *", and uses "count >>2", and the code
after also casts to "u32 *", what about getting rid of all casts like:
u32 data = 0;
u32 *buf32 = buf;
if (is_read)
sd_ctrl_read32_rep(host, CTL_SD_DATA_PORT, buf32,
count >> 2);
else
sd_ctrl_write32_rep(host, CTL_SD_DATA_PORT, buf32,
count >> 2);
/* if count was multiple of 4 */
if (!(count & 0x3))
return;
buf32 += count >> 2;
count %= 4;
if (is_read) {
sd_ctrl_read32_rep(host, CTL_SD_DATA_PORT, &data, 1);
memcpy(buf32, &data, count);
} else {
memcpy(&data, buf32, count);
sd_ctrl_write32_rep(host, CTL_SD_DATA_PORT, &data, 1);
}
return;
}
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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