Hi Geert,
Thank you for your review!
> -----Original Message-----
> From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> Sent: Tuesday, October 05, 2021 4:32 PM
> To: Gabbasov, Andrew <Andrew_Gabbasov@xxxxxxxxxx>
> Cc: Linux-Renesas <linux-renesas-soc@xxxxxxxxxxxxxxx>; Linux I2C <linux-i2c@xxxxxxxxxxxxxxx>; Linux Kernel
> Mailing List <linux-kernel@xxxxxxxxxxxxxxx>; Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>; Surachari,
> Bhuvanesh <Bhuvanesh_Surachari@xxxxxxxxxx>
> Subject: Re: [PATCH] i2c: rcar: add SMBus block read support
>
> Hi Andrew,
>
> On Wed, Sep 22, 2021 at 6:14 PM Andrew Gabbasov
> <andrew_gabbasov@xxxxxxxxxx> wrote:
> > The smbus block read is not currently supported for rcar i2c devices.
> > This patchset adds the support to rcar i2c bus so that blocks of data
> > can be read using SMbus block reads.(using i2c_smbus_read_block_data()
> > function from the i2c-core-smbus.c).
> >
> > Inspired by commit 8e8782c71595 ("i2c: imx: add SMBus block read support")
> >
> > This patch (adapted) was tested with v4.14, but due to lack of real
> > hardware with SMBus block read operations support, using "simulation",
> > that is manual analysis of data, read from plain I2C devices with
> > SMBus block read request.
> >
> > Signed-off-by: Bhuvanesh Surachari <bhuvanesh_surachari@xxxxxxxxxx>
> > Signed-off-by: Andrew Gabbasov <andrew_gabbasov@xxxxxxxxxx>
>
> Thanks for your patch!
>
> > --- a/drivers/i2c/busses/i2c-rcar.c
> > +++ b/drivers/i2c/busses/i2c-rcar.c
> > @@ -429,9 +431,16 @@ static bool rcar_i2c_dma(struct rcar_i2c_priv *priv)
> > /*
> > * The last two bytes needs to be fetched using PIO in
> > * order for the STOP phase to work.
> > + *
> > + * For SMBus block read the first byte was received using PIO.
>
> So it might be easier to read, and more maintainable, to keep the
> old assignments:
>
> buf = priv->msg->buf;
> len = priv->msg->len - 2;
>
> and adjust them for SMBus afterwards:
>
> if (block_data) {
> /* For SMBus block read the first byte was received using PIO */
> buf++;
> len--;
> }
>
> ?
>
> > */
> > - buf = priv->msg->buf;
> > - len = priv->msg->len - 2;
> > + if (block_data) {
> > + buf = priv->msg->buf + 1;
> > + len = priv->msg->len - 3;
> > + } else {
> > + buf = priv->msg->buf;
> > + len = priv->msg->len - 2;
> > + }
> > } else {
> > /*
> > * First byte in message was sent using PIO.
>
> And below we have another case handling buf and len :-(
>
> So perhaps:
>
> buf = priv->msg->buf;
> len = priv->msg->len;
>
> if (read) {
> /*
> * The last two bytes needs to be fetched using PIO in
> * order for the STOP phase to work.
> */
> len -= 2;
> }
> if (!read || block_data) {
> /* First byte in message was sent using PIO *
> buf++;
> len--;
> }
Probably I was trying to minimize the changes ;-)
However, I agree with you that the whole code fragment can be simplified
and your variant indeed looks more clean and understandable.
Thank you for your suggestion, I'll submit version 2 of the patch
with this fragment changed.
Thanks!
Best regards,
Andrew
