[PATCH] mfd: cros_ec: check for NULL transfer function

[PATCH] mfd: cros_ec: check for NULL transfer function

[egranata]

From: Enrico Granata <egranata@chromium.org>

As new transfer mechanisms are added to the EC codebase, they may
not support v2 of the EC protocol.

If the v3 initial handshake transfer fails, the kernel will try
and call cmd_xfer as a fallback. If v2 is not supported, cmd_xfer
will be NULL, and the code will end up causing a kernel panic.

Add a check for NULL before calling the transfer function, along
with a helpful comment explaining how one might end up in this
situation.

Signed-off-by: Enrico Granata <egranata@chromium.org>
---
 drivers/platform/chrome/cros_ec_proto.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index 97a068dff192d..953076ab401aa 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -56,6 +56,16 @@ static int send_command(struct cros_ec_device *ec_dev,
 	else
 		xfer_fxn = ec_dev->cmd_xfer;
 
+	if (xfer_fxn == NULL) {
+		/* This error can happen if a communication error happened and
+		 * the EC is trying to use protocol v2, on an underlying
+		 * communication mechanism that does not support v2.
+		 */
+		dev_err(ec_dev->dev,
+			"missing EC transfer API, cannot send command\n");
+		return -EIO;
+	}
+
 	ret = (*xfer_fxn)(ec_dev, msg);
 	if (msg->result == EC_RES_IN_PROGRESS) {
 		int i;
-- 
2.21.0.392.gf8f6787159e-goog

Re: [PATCH] mfd: cros_ec: check for NULL transfer function

[Guenter Roeck]

On Wed, Apr 3, 2019 at 11:31 AM <egranata@chromium.org> wrote:
>
> From: Enrico Granata <egranata@chromium.org>
>
> As new transfer mechanisms are added to the EC codebase, they may
> not support v2 of the EC protocol.
>
> If the v3 initial handshake transfer fails, the kernel will try
> and call cmd_xfer as a fallback. If v2 is not supported, cmd_xfer
> will be NULL, and the code will end up causing a kernel panic.
>
> Add a check for NULL before calling the transfer function, along
> with a helpful comment explaining how one might end up in this
> situation.
>
> Signed-off-by: Enrico Granata <egranata@chromium.org>
> ---
>  drivers/platform/chrome/cros_ec_proto.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index 97a068dff192d..953076ab401aa 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -56,6 +56,16 @@ static int send_command(struct cros_ec_device *ec_dev,
>         else
>                 xfer_fxn = ec_dev->cmd_xfer;
>
> +       if (xfer_fxn == NULL) {
> +               /* This error can happen if a communication error happened and
> +                * the EC is trying to use protocol v2, on an underlying
> +                * communication mechanism that does not support v2.
> +                */

I am not personally a friend of networking-style multi-line comments.

> +               dev_err(ec_dev->dev,
> +                       "missing EC transfer API, cannot send command\n");

That message will be displayed each time a message is sent, ie in
practice for each message. Is there any value in that, other than
clogging the log ?

Guenter

> +               return -EIO;
> +       }
> +
>         ret = (*xfer_fxn)(ec_dev, msg);
>         if (msg->result == EC_RES_IN_PROGRESS) {
>                 int i;
> --
> 2.21.0.392.gf8f6787159e-goog
>

Re: [PATCH] mfd: cros_ec: check for NULL transfer function

[Enrico Granata]

I can certainly add a "did_print_error" flag or some such, but in
practice, if the transfer function is NULL, the initial handshake will
fail, and this will in turn cause EC registration to fail, and no
further communication should occur, so no further log entries will be
printed.

Thanks

Enrico Granata | egranata@google.com | ChromeOS | MTV1600


On Wed, Apr 3, 2019 at 11:51 AM Guenter Roeck <groeck@google.com> wrote:
>
> On Wed, Apr 3, 2019 at 11:31 AM <egranata@chromium.org> wrote:
> >
> > From: Enrico Granata <egranata@chromium.org>
> >
> > As new transfer mechanisms are added to the EC codebase, they may
> > not support v2 of the EC protocol.
> >
> > If the v3 initial handshake transfer fails, the kernel will try
> > and call cmd_xfer as a fallback. If v2 is not supported, cmd_xfer
> > will be NULL, and the code will end up causing a kernel panic.
> >
> > Add a check for NULL before calling the transfer function, along
> > with a helpful comment explaining how one might end up in this
> > situation.
> >
> > Signed-off-by: Enrico Granata <egranata@chromium.org>
> > ---
> >  drivers/platform/chrome/cros_ec_proto.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> > index 97a068dff192d..953076ab401aa 100644
> > --- a/drivers/platform/chrome/cros_ec_proto.c
> > +++ b/drivers/platform/chrome/cros_ec_proto.c
> > @@ -56,6 +56,16 @@ static int send_command(struct cros_ec_device *ec_dev,
> >         else
> >                 xfer_fxn = ec_dev->cmd_xfer;
> >
> > +       if (xfer_fxn == NULL) {
> > +               /* This error can happen if a communication error happened and
> > +                * the EC is trying to use protocol v2, on an underlying
> > +                * communication mechanism that does not support v2.
> > +                */
>
> I am not personally a friend of networking-style multi-line comments.
>
> > +               dev_err(ec_dev->dev,
> > +                       "missing EC transfer API, cannot send command\n");
>
> That message will be displayed each time a message is sent, ie in
> practice for each message. Is there any value in that, other than
> clogging the log ?
>
> Guenter
>
> > +               return -EIO;
> > +       }
> > +
> >         ret = (*xfer_fxn)(ec_dev, msg);
> >         if (msg->result == EC_RES_IN_PROGRESS) {
> >                 int i;
> > --
> > 2.21.0.392.gf8f6787159e-goog
> >

Re: [PATCH] mfd: cros_ec: check for NULL transfer function

[Guenter Roeck]

On Wed, Apr 3, 2019 at 12:40 PM Enrico Granata <egranata@google.com> wrote:
>
> I can certainly add a "did_print_error" flag or some such, but in practice, if the transfer function is NULL, the initial handshake will fail, and this will in turn cause EC registration to fail, and no further communication should occur, so no further log entries will be printed.
>
Sorry, I am a bit lost. Why would dev_err_once() not work ?

Guenter

> Thanks
>
> Enrico Granata | egranata@google.com | ChromeOS | MTV1600
>
>
> On Wed, Apr 3, 2019 at 11:51 AM Guenter Roeck <groeck@google.com> wrote:
>>
>> On Wed, Apr 3, 2019 at 11:31 AM <egranata@chromium.org> wrote:
>> >
>> > From: Enrico Granata <egranata@chromium.org>
>> >
>> > As new transfer mechanisms are added to the EC codebase, they may
>> > not support v2 of the EC protocol.
>> >
>> > If the v3 initial handshake transfer fails, the kernel will try
>> > and call cmd_xfer as a fallback. If v2 is not supported, cmd_xfer
>> > will be NULL, and the code will end up causing a kernel panic.
>> >
>> > Add a check for NULL before calling the transfer function, along
>> > with a helpful comment explaining how one might end up in this
>> > situation.
>> >
>> > Signed-off-by: Enrico Granata <egranata@chromium.org>
>> > ---
>> >  drivers/platform/chrome/cros_ec_proto.c | 10 ++++++++++
>> >  1 file changed, 10 insertions(+)
>> >
>> > diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
>> > index 97a068dff192d..953076ab401aa 100644
>> > --- a/drivers/platform/chrome/cros_ec_proto.c
>> > +++ b/drivers/platform/chrome/cros_ec_proto.c
>> > @@ -56,6 +56,16 @@ static int send_command(struct cros_ec_device *ec_dev,
>> >         else
>> >                 xfer_fxn = ec_dev->cmd_xfer;
>> >
>> > +       if (xfer_fxn == NULL) {
>> > +               /* This error can happen if a communication error happened and
>> > +                * the EC is trying to use protocol v2, on an underlying
>> > +                * communication mechanism that does not support v2.
>> > +                */
>>
>> I am not personally a friend of networking-style multi-line comments.
>>
>> > +               dev_err(ec_dev->dev,
>> > +                       "missing EC transfer API, cannot send command\n");
>>
>> That message will be displayed each time a message is sent, ie in
>> practice for each message. Is there any value in that, other than
>> clogging the log ?
>>
>> Guenter
>>
>> > +               return -EIO;
>> > +       }
>> > +
>> >         ret = (*xfer_fxn)(ec_dev, msg);
>> >         if (msg->result == EC_RES_IN_PROGRESS) {
>> >                 int i;
>> > --
>> > 2.21.0.392.gf8f6787159e-goog
>> >

Re: [PATCH] mfd: cros_ec: check for NULL transfer function

[Enrico Granata]

Because I did not know about it till right now. Thanks for the
suggestion. Will upload a v2 as soon as I get a chance.

On Wed, Apr 3, 2019 at 12:53 PM Guenter Roeck <groeck@google.com> wrote:
>
> On Wed, Apr 3, 2019 at 12:40 PM Enrico Granata <egranata@google.com> wrote:
> >
> > I can certainly add a "did_print_error" flag or some such, but in practice, if the transfer function is NULL, the initial handshake will fail, and this will in turn cause EC registration to fail, and no further communication should occur, so no further log entries will be printed.
> >
> Sorry, I am a bit lost. Why would dev_err_once() not work ?
>
> Guenter
>
> > Thanks
> >
> > Enrico Granata | egranata@google.com | ChromeOS | MTV1600
> >
> >
> > On Wed, Apr 3, 2019 at 11:51 AM Guenter Roeck <groeck@google.com> wrote:
> >>
> >> On Wed, Apr 3, 2019 at 11:31 AM <egranata@chromium.org> wrote:
> >> >
> >> > From: Enrico Granata <egranata@chromium.org>
> >> >
> >> > As new transfer mechanisms are added to the EC codebase, they may
> >> > not support v2 of the EC protocol.
> >> >
> >> > If the v3 initial handshake transfer fails, the kernel will try
> >> > and call cmd_xfer as a fallback. If v2 is not supported, cmd_xfer
> >> > will be NULL, and the code will end up causing a kernel panic.
> >> >
> >> > Add a check for NULL before calling the transfer function, along
> >> > with a helpful comment explaining how one might end up in this
> >> > situation.
> >> >
> >> > Signed-off-by: Enrico Granata <egranata@chromium.org>
> >> > ---
> >> >  drivers/platform/chrome/cros_ec_proto.c | 10 ++++++++++
> >> >  1 file changed, 10 insertions(+)
> >> >
> >> > diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> >> > index 97a068dff192d..953076ab401aa 100644
> >> > --- a/drivers/platform/chrome/cros_ec_proto.c
> >> > +++ b/drivers/platform/chrome/cros_ec_proto.c
> >> > @@ -56,6 +56,16 @@ static int send_command(struct cros_ec_device *ec_dev,
> >> >         else
> >> >                 xfer_fxn = ec_dev->cmd_xfer;
> >> >
> >> > +       if (xfer_fxn == NULL) {
> >> > +               /* This error can happen if a communication error happened and
> >> > +                * the EC is trying to use protocol v2, on an underlying
> >> > +                * communication mechanism that does not support v2.
> >> > +                */
> >>
> >> I am not personally a friend of networking-style multi-line comments.
> >>
> >> > +               dev_err(ec_dev->dev,
> >> > +                       "missing EC transfer API, cannot send command\n");
> >>
> >> That message will be displayed each time a message is sent, ie in
> >> practice for each message. Is there any value in that, other than
> >> clogging the log ?
> >>
> >> Guenter
> >>
> >> > +               return -EIO;
> >> > +       }
> >> > +
> >> >         ret = (*xfer_fxn)(ec_dev, msg);
> >> >         if (msg->result == EC_RES_IN_PROGRESS) {
> >> >                 int i;
> >> > --
> >> > 2.21.0.392.gf8f6787159e-goog
> >> >

[PATCH v2] mfd: cros_ec: check for NULL transfer function

[egranata]

From: Enrico Granata <egranata@chromium.org>

As new transfer mechanisms are added to the EC codebase, they may
not support v2 of the EC protocol.

If the v3 initial handshake transfer fails, the kernel will try
and call cmd_xfer as a fallback. If v2 is not supported, cmd_xfer
will be NULL, and the code will end up causing a kernel panic.

Add a check for NULL before calling the transfer function, along
with a helpful comment explaining how one might end up in this
situation.

Signed-off-by: Enrico Granata <egranata@chromium.org>
---
 drivers/platform/chrome/cros_ec_proto.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index 97a068dff192d..55691656a3c27 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -56,6 +56,16 @@ static int send_command(struct cros_ec_device *ec_dev,
 	else
 		xfer_fxn = ec_dev->cmd_xfer;
 
+	if (xfer_fxn == NULL) {
+		/* This error can happen if a communication error happened and
+		 * the EC is trying to use protocol v2, on an underlying
+		 * communication mechanism that does not support v2.
+		 */
+		dev_err_once(ec_dev->dev,
+			"missing EC transfer API, cannot send command\n");
+		return -EIO;
+	}
+
 	ret = (*xfer_fxn)(ec_dev, msg);
 	if (msg->result == EC_RES_IN_PROGRESS) {
 		int i;
-- 
2.21.0.392.gf8f6787159e-goog

Re: [PATCH v2] mfd: cros_ec: check for NULL transfer function

[Jett ✈ Rink]

Reviewed-by: Jett Rink <jettrink@chromium.org>

On Wed, Apr 3, 2019 at 4:40 PM <egranata@chromium.org> wrote:
>
> From: Enrico Granata <egranata@chromium.org>
>
> As new transfer mechanisms are added to the EC codebase, they may
> not support v2 of the EC protocol.
>
> If the v3 initial handshake transfer fails, the kernel will try
> and call cmd_xfer as a fallback. If v2 is not supported, cmd_xfer
> will be NULL, and the code will end up causing a kernel panic.
>
> Add a check for NULL before calling the transfer function, along
> with a helpful comment explaining how one might end up in this
> situation.
>
> Signed-off-by: Enrico Granata <egranata@chromium.org>
> ---
>  drivers/platform/chrome/cros_ec_proto.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index 97a068dff192d..55691656a3c27 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -56,6 +56,16 @@ static int send_command(struct cros_ec_device *ec_dev,
>         else
>                 xfer_fxn = ec_dev->cmd_xfer;
>
> +       if (xfer_fxn == NULL) {
> +               /* This error can happen if a communication error happened and
> +                * the EC is trying to use protocol v2, on an underlying
> +                * communication mechanism that does not support v2.
> +                */
> +               dev_err_once(ec_dev->dev,
> +                       "missing EC transfer API, cannot send command\n");
> +               return -EIO;
> +       }
> +
>         ret = (*xfer_fxn)(ec_dev, msg);
>         if (msg->result == EC_RES_IN_PROGRESS) {
>                 int i;
> --
> 2.21.0.392.gf8f6787159e-goog
>

Re: [PATCH v2] mfd: cros_ec: check for NULL transfer function

[Enric Balletbo i Serra]

Hi Enrico,

Many thanks to send this upstream.

On 4/4/19 18:00, Jett ✈ Rink wrote:
> Reviewed-by: Jett Rink <jettrink@chromium.org>
> 
> On Wed, Apr 3, 2019 at 4:40 PM <egranata@chromium.org> wrote:
>>
>> From: Enrico Granata <egranata@chromium.org>
>>
>> As new transfer mechanisms are added to the EC codebase, they may
>> not support v2 of the EC protocol.
>>
>> If the v3 initial handshake transfer fails, the kernel will try
>> and call cmd_xfer as a fallback. If v2 is not supported, cmd_xfer
>> will be NULL, and the code will end up causing a kernel panic.
>>
>> Add a check for NULL before calling the transfer function, along
>> with a helpful comment explaining how one might end up in this
>> situation.
>>
>> Signed-off-by: Enrico Granata <egranata@chromium.org>
>> ---
>>  drivers/platform/chrome/cros_ec_proto.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
>> index 97a068dff192d..55691656a3c27 100644
>> --- a/drivers/platform/chrome/cros_ec_proto.c
>> +++ b/drivers/platform/chrome/cros_ec_proto.c
>> @@ -56,6 +56,16 @@ static int send_command(struct cros_ec_device *ec_dev,
>>         else
>>                 xfer_fxn = ec_dev->cmd_xfer;
>>
>> +       if (xfer_fxn == NULL) {
>> +               /* This error can happen if a communication error happened and

Like Guenter I personally don't like the networking-style multi-line comments.
We try to use the default kernel-style so if you don't mind I'll change this.


>> +                * the EC is trying to use protocol v2, on an underlying
>> +                * communication mechanism that does not support v2.
>> +                */
>> +               dev_err_once(ec_dev->dev,
>> +                       "missing EC transfer API, cannot send command\n");
>> +               return -EIO;
>> +       }
>> +
>>         ret = (*xfer_fxn)(ec_dev, msg);
>>         if (msg->result == EC_RES_IN_PROGRESS) {
>>                 int i;
>> --
>> 2.21.0.392.gf8f6787159e-goog
>>

I'll add the patch to the for-next branch in chrome-platform repository for
auto-builders to play with. If all goes well I'll queue the patch for
chrome-platform-5.2.

Thanks,
 Enric