[PATCH v10 04/27] spi: spi-mem: add spi_mem_dtr_supports_op()

[Pratyush Yadav]

On 26/06/21 02:44PM, Jagan Teki wrote:
> On Sat, Jun 26, 2021 at 12:47 AM Pratyush Yadav <p.yadav at ti.com> wrote:
> >
> > spi_mem_default_supports_op() rejects DTR ops by default to ensure that
> > the controller drivers that haven't been updated with DTR support
> > continue to reject them. It also makes sure that controllers that don't
> > support DTR mode at all (which is most of them at the moment) also
> > reject them.
> >
> > This means that controller drivers that want to support DTR mode can't
> > use spi_mem_default_supports_op(). Driver authors have to roll their own
> > supports_op() function and mimic the buswidth checks. Or even worse,
> > driver authors might skip it completely or get it wrong.
> >
> > Add spi_mem_dtr_supports_op(). It provides a basic sanity check for DTR
> > ops and performs the buswidth requirement check. Move the logic for
> > checking buswidth in spi_mem_default_supports_op() to a separate
> > function so the logic is not repeated twice.
> >
> > Signed-off-by: Pratyush Yadav <p.yadav at ti.com>
> > ---
> >  drivers/spi/spi-mem.c | 32 +++++++++++++++++++++++++++++---
> >  include/spi-mem.h     |  2 ++
> >  2 files changed, 31 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> > index 541cd0e5a7..9c1ede1b61 100644
> > --- a/drivers/spi/spi-mem.c
> > +++ b/drivers/spi/spi-mem.c
> > @@ -145,8 +145,8 @@ static int spi_check_buswidth_req(struct spi_slave *slave, u8 buswidth, bool tx)
> >         return -ENOTSUPP;
> >  }
> >
> > -bool spi_mem_default_supports_op(struct spi_slave *slave,
> > -                                const struct spi_mem_op *op)
> > +static bool spi_mem_check_buswidth(struct spi_slave *slave,
> > +                                  const struct spi_mem_op *op)
> >  {
> >         if (spi_check_buswidth_req(slave, op->cmd.buswidth, true))
> >                 return false;
> > @@ -164,13 +164,39 @@ bool spi_mem_default_supports_op(struct spi_slave *slave,
> >                                    op->data.dir == SPI_MEM_DATA_OUT))
> >                 return false;
> >
> > +       return true;
> > +}
> > +
> > +bool spi_mem_dtr_supports_op(struct spi_slave *slave,
> > +                            const struct spi_mem_op *op)
> > +{
> > +       if (op->cmd.buswidth == 8 && op->cmd.nbytes % 2)
> > +               return false;
> > +
> > +       if (op->addr.nbytes && op->addr.buswidth == 8 && op->addr.nbytes % 2)
> > +               return false;
> > +
> > +       if (op->dummy.nbytes && op->dummy.buswidth == 8 && op->dummy.nbytes % 2)
> > +               return false;
> > +
> > +       if (op->data.dir != SPI_MEM_NO_DATA &&
> > +           op->dummy.buswidth == 8 && op->data.nbytes % 2)
> > +               return false;
> > +
> > +       return spi_mem_check_buswidth(slave, op);
> > +}
> > +EXPORT_SYMBOL_GPL(spi_mem_dtr_supports_op);
> 
> Does this export_symbol is used in U-Boot?

It is being used in drivers ported from Linux. I see it being used in 
spi-mem.c, mtdcore.c, x530_cert_parser.c, nand/core.c, etc. It is 
defined to an empty macro in include/linux/compat.h.

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.