Re: [PATCH 1/4] platform/chrome: Add EC command msg wrapper

[Prashant Malani]

Hi Enric,

On Mon, Jan 27, 2020 at 7:29 AM Enric Balletbo i Serra
<enric.balletbo@xxxxxxxxxxxxx> wrote:
>
> Hi Prashant,
>
> Many thanks for this patch.
>
> On 25/1/20 2:21, Prashant Malani wrote:
> > Many callers of cros_ec_cmd_xfer_status() use a similar set up of
> > allocating and filling a message buffer and then copying any received
> > data to a target buffer.
> >
>
> cros_ec_cmd_xfer_status is already a wrapper, I dislike the idea of having three
> ways to do the same (cros_ec_cmd_xfer, cros_ec_cmd_xfer_status and this new
> one). I like the idea of have a wrapper that embeds the message allocation but
> we should not confuse users with different calls that does the same.
Yes, my intention was to eventually replace all the xfer_status()
call-sites to use the new wrapper, and then get rid of xfer_status
completely.
>
> So, I am for a change like this but I'd like to have all the users calling the
> same wrapper (unless there is a good reason to not use it). A proposed roadmap
> (to be discussed) for this would be.
>
> 1. Replace all the remaining "cros_ec_cmd_xfer" calls with
> "cros_ec_cmd_xfer_status".
> 2. Modify cros_ec_cmd_xfer_status to embed the message allocation.

How about the following alteration the the roadmap:
- Introducing the new wrapper.
- Replacing all remaining cros_ec_cmd_xfer/cros_ec_cmd_xfer_status to
use the new wrapper.
- Deleting cros_ec_cmd_xfer and cros_ec_cmd_xfer_status ?
My thinking is that this would mean fewer changes at the call-sites
compared to the original roadmap (in the original roadmap, one would
first have to modify calls to use cros_ec_cmd_xfer_status(), and then
modify them again when cros_ec_cmd_xfer_status() itself is modified to
include message allocation).

That said I don't have any strong preference, so either would work.

Best regards,
>
> Thanks,
>  Enric
>
>
> > Create a utility function that performs this setup so that callers can
> > use this function instead.
> >
> > Signed-off-by: Prashant Malani <pmalani@xxxxxxxxxxxx>
> > ---
> >  drivers/platform/chrome/cros_ec_proto.c     | 53 +++++++++++++++++++++
> >  include/linux/platform_data/cros_ec_proto.h |  5 ++
> >  2 files changed, 58 insertions(+)
> >
> > diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> > index da1b1c4504333..8ef3b7d27d260 100644
> > --- a/drivers/platform/chrome/cros_ec_proto.c
> > +++ b/drivers/platform/chrome/cros_ec_proto.c
> > @@ -5,6 +5,7 @@
> >
> >  #include <linux/delay.h>
> >  #include <linux/device.h>
> > +#include <linux/mfd/cros_ec.h>
> >  #include <linux/module.h>
> >  #include <linux/platform_data/cros_ec_commands.h>
> >  #include <linux/platform_data/cros_ec_proto.h>
> > @@ -570,6 +571,58 @@ int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
> >  }
> >  EXPORT_SYMBOL(cros_ec_cmd_xfer_status);
> >
> > +/**
> > + * cros_ec_send_cmd_msg() - Utility function to send commands to ChromeOS EC.
> > + * @ec: EC device struct.
> > + * @version: Command version number (often 0).
> > + * @command: Command ID including offset.
> > + * @outdata: Data to be sent to the EC.
> > + * @outsize: Size of the &outdata buffer.
> > + * @indata: Data to be received from the EC.
> > + * @insize: Size of the &indata buffer.
> > + *
> > + * This function is a wrapper around &cros_ec_cmd_xfer_status, and performs
> > + * some of the common work involved with sending a command to the EC. This
> > + * includes allocating and filling up a &struct cros_ec_command message buffer,
> > + * and copying the received data to another buffer.
> > + *
> > + * Return: The number of bytes transferred on success or negative error code.
> > + */
> > +int cros_ec_send_cmd_msg(struct cros_ec_device *ec, unsigned int version,
> > +                      unsigned int command, void *outdata,
> > +                      unsigned int outsize, void *indata,
> > +                      unsigned int insize)
> > +{
> > +     struct cros_ec_command *msg;
> > +     int ret;
> > +
> > +     msg = kzalloc(sizeof(*msg) + max(outsize, insize), GFP_KERNEL);
> > +     if (!msg)
> > +             return -ENOMEM;
> > +
> > +     msg->version = version;
> > +     msg->command = command;
> > +     msg->outsize = outsize;
> > +     msg->insize = insize;
> > +
> > +     if (outdata && outsize > 0)
> > +             memcpy(msg->data, outdata, outsize);
> > +
> > +     ret = cros_ec_cmd_xfer_status(ec, msg);
> > +     if (ret < 0) {
> > +             dev_warn(ec->dev, "Command failed: %d\n", msg->result);
> > +             goto cleanup;
> > +     }
> > +
> > +     if (insize)
> > +             memcpy(indata, msg->data, insize);
> > +
> > +cleanup:
> > +     kfree(msg);
> > +     return ret;
> > +}
> > +EXPORT_SYMBOL(cros_ec_send_cmd_msg);
> > +
> >  static int get_next_event_xfer(struct cros_ec_device *ec_dev,
> >                              struct cros_ec_command *msg,
> >                              struct ec_response_get_next_event_v1 *event,
> > diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> > index 30098a5515231..166ce26bdd79e 100644
> > --- a/include/linux/platform_data/cros_ec_proto.h
> > +++ b/include/linux/platform_data/cros_ec_proto.h
> > @@ -201,6 +201,11 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
> >  int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
> >                           struct cros_ec_command *msg);
> >
> > +int cros_ec_send_cmd_msg(struct cros_ec_device *ec_dev, unsigned int version,
> > +                      unsigned int command, void *outdata,
> > +                      unsigned int outsize, void *indata,
> > +                      unsigned int insize);
> > +
> >  int cros_ec_register(struct cros_ec_device *ec_dev);
> >
> >  int cros_ec_unregister(struct cros_ec_device *ec_dev);
> >