On Mon, 2020-05-18 at 14:38 +0100, Dave Stevenson wrote:
> Hi Nicholas
>
> Sorry for the slight delay in replying.
>
> On Mon, 11 May 2020 at 20:19, Nicolas Saenz Julienne
> <nsaenzjulienne@xxxxxxx> wrote:
> > Hi Naushir,
> > a small comment.
> >
> > On Mon, 2020-05-04 at 12:26 +0300, Laurent Pinchart wrote:
> > > From: Naushir Patuck <naush@xxxxxxxxxxxxxxx>
> > >
> > > Port the V4L2 compatible driver for the ISP unit found on Broadcom BCM2835
> > > chips.
> > >
> > > The driver interfaces though the VideoCore unit using the VCHIQ MMAL
> > > interface.
> > >
> > > ISP driver upported from from RaspberryPi BSP at revision:
> > > 6c3505be6c3e ("staging: vc04_services: isp: Make all references to
> > > bcm2835_isp_fmt const")
> > >
> > > Signed-off-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Naushir Patuck <naush@xxxxxxxxxxxxxxx>
> > > [Adapt to staging by moving all modifications that in the BSP are
> > > scattered
> > > in core components inside this directory]
> > > Signed-off-by: Jacopo Mondi <jacopo@xxxxxxxxxx>
> > > ---
> >
> > [...]
> >
> > > +static int bcm2835_isp_mmal_buf_cleanup(struct mmal_buffer *mmal_buf)
> > > +{
> > > + mmal_vchi_buffer_cleanup(mmal_buf);
> > > +
> > > + if (mmal_buf->dma_buf) {
> > > + dma_buf_put(mmal_buf->dma_buf);
> > > + mmal_buf->dma_buf = NULL;
> >
> > Why is this needed here, shouldn't this be mmal-vchi's responsibility? IIUC
> > the
> > original dma_buf_get() happens there too.
>
> The original dma_buf_get is in bcm2835_isp_buf_prepare as it either
> comes from a dma_buf_get(vb->planes[0].m.fd) for VB2_MEMORY_DMABUF
> operations, or a vb2_core_expbuf_dmabuf for VB2_MEMORY_MMAP.
> Seeing as the original "get" is in this calling code, it seemed
> reasonable that the put is as well.
>
> There are no get/put operations on dma-bufs (other than indirectly
> through vc_sm_cma) within mmal-vchiq. You have the call
> vc_sm_cma_import_dmabuf to take the external dma_buf and pull it into
> vc_sm_cma, but that is the limit of it.
Understood, thanks.
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