Re: [PATCH] i2c: at91: use dma safe buffers

[Michael Walle]

Am 2022-04-05 12:02, schrieb Codrin.Ciubotariu@xxxxxxxxxxxxx:
> On 05.04.2022 12:38, Michael Walle wrote:
> > Am 2022-04-05 11:23, schrieb Codrin.Ciubotariu@xxxxxxxxxxxxx:
> > > > +       if (dev->use_dma) {
> > > > +               dma_buf = i2c_get_dma_safe_msg_buf(m_start, 1);
> > >
> > > If you want, you could just dev->buf = i2c_get_dma_safe...
> >
> > But where is the error handling in that case? dev->buf will
> > be NULL, which is eventually passed to dma_map_single().
> >
> > Also, I need the dma_buf for the i2c_put_dma_safe_msg_buf()
> > call anyway, because dev->buf will be modified during
> > processing.
>
> You still:
> 	if (!dev->buf) {
> 		ret = -ENOMEM;
> 		goto out;
> 	}
>
> So, at91_do_twi_transfer()/dma_map_single() will not be called.

Ahh, I misunderstood you. Yes, but as I said, I need the dma_buf
temporary variable anyway, because dev->buf is modified, eg. see
at91_twi_read_data_dma_callback().

-michael