[PATCH] i2c: rk3x: fix 0 length write transfers

[PATCH] i2c: rk3x: fix 0 length write transfers

[Alexandru M Stan]

i2cdetect -q was broken (everything was a false positive, and no transfers were
actually being sent over i2c). The way it works is by sending a 0 length write
request and checking for NACK. This patch fixes the 0 length writes and actually
sends them.

Reported-by: Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Signed-off-by: Alexandru M Stan <amstan-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
---
 drivers/i2c/busses/i2c-rk3x.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
index b41d979..f486d0e 100644
--- a/drivers/i2c/busses/i2c-rk3x.c
+++ b/drivers/i2c/busses/i2c-rk3x.c
@@ -238,7 +238,7 @@ static void rk3x_i2c_fill_transmit_buf(struct rk3x_i2c *i2c)
 	for (i = 0; i < 8; ++i) {
 		val = 0;
 		for (j = 0; j < 4; ++j) {
-			if (i2c->processed == i2c->msg->len)
+			if ((i2c->processed == i2c->msg->len) && (cnt != 0))
 				break;
 
 			if (i2c->processed == 0 && cnt == 0)
-- 
2.1.0.rc2.206.gedb03e5

Re: [PATCH] i2c: rk3x: fix 0 length write transfers

[Doug Anderson]

Alex,

On Wed, Oct 1, 2014 at 10:40 AM, Alexandru M Stan <amstan-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org> wrote:
> i2cdetect -q was broken (everything was a false positive, and no transfers were
> actually being sent over i2c). The way it works is by sending a 0 length write
> request and checking for NACK. This patch fixes the 0 length writes and actually
> sends them.
>
> Reported-by: Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> Signed-off-by: Alexandru M Stan <amstan-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> ---
>  drivers/i2c/busses/i2c-rk3x.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
> index b41d979..f486d0e 100644
> --- a/drivers/i2c/busses/i2c-rk3x.c
> +++ b/drivers/i2c/busses/i2c-rk3x.c
> @@ -238,7 +238,7 @@ static void rk3x_i2c_fill_transmit_buf(struct rk3x_i2c *i2c)
>         for (i = 0; i < 8; ++i) {
>                 val = 0;
>                 for (j = 0; j < 4; ++j) {
> -                       if (i2c->processed == i2c->msg->len)
> +                       if ((i2c->processed == i2c->msg->len) && (cnt != 0))

This looks good to me.  Basically we still need to write the address
of the device onto the bus even if there's no data.

Reviewed-by: Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Tested-by: Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>

-Doug

Re: [PATCH] i2c: rk3x: fix 0 length write transfers

[Max Schwarz]

Hi Alexandru,

On Wednesday 01 October 2014 at 10:40:41, Alexandru M Stan wrote:
> i2cdetect -q was broken (everything was a false positive, and no transfers
> were actually being sent over i2c). The way it works is by sending a 0
> length write request and checking for NACK. This patch fixes the 0 length
> writes and actually sends them.
> 
> Reported-by: Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> Signed-off-by: Alexandru M Stan <amstan-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> ---
>  drivers/i2c/busses/i2c-rk3x.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
> index b41d979..f486d0e 100644
> --- a/drivers/i2c/busses/i2c-rk3x.c
> +++ b/drivers/i2c/busses/i2c-rk3x.c
> @@ -238,7 +238,7 @@ static void rk3x_i2c_fill_transmit_buf(struct rk3x_i2c
> *i2c) for (i = 0; i < 8; ++i) {
>  		val = 0;
>  		for (j = 0; j < 4; ++j) {
> -			if (i2c->processed == i2c->msg->len)
> +			if ((i2c->processed == i2c->msg->len) && (cnt != 0))
>  				break;
> 
>  			if (i2c->processed == 0 && cnt == 0)

Yes, looks correct and makes i2cdetect work for me on Radxa Rock.

Reviewed-By: Max Schwarz <max.schwarz-BGeptl67XyCzQB+pC5nmwQ@public.gmane.org>
Tested-By: Max Schwarz <max.schwarz-BGeptl67XyCzQB+pC5nmwQ@public.gmane.org>

Cheers,
  Max

Re: [PATCH] i2c: rk3x: fix 0 length write transfers

[Wolfram Sang]

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> Reviewed-By: Max Schwarz <max.schwarz@online.de>
> Tested-By: Max Schwarz <max.schwarz@online.de>

Checkpatch says: 

WARNING: 'Tested-by:' is the preferred signature form

Same 'Reviewed-by:'

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Re: [PATCH] i2c: rk3x: fix 0 length write transfers

[Wolfram Sang]

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On Wed, Oct 01, 2014 at 10:40:41AM -0700, Alexandru M Stan wrote:
> i2cdetect -q was broken (everything was a false positive, and no transfers were
> actually being sent over i2c). The way it works is by sending a 0 length write
> request and checking for NACK. This patch fixes the 0 length writes and actually
> sends them.
> 
> Reported-by: Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> Signed-off-by: Alexandru M Stan <amstan-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>

Applied to for-current, thanks!


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