Hi Arnd, On Mon, 22 Sep 2014 21:45:40 +0200 Arnd Bergmann <[email protected]> wrote:
> On Monday 22 September 2014 21:37:55 Boris BREZILLON wrote: > > dma_mask and dma_parms are already inherited from the parent device but > > dma_coherent_mask was left uninitialized (set to zero thanks to kzalloc). > > Set sub-device coherent_dma_mask to its parent value to simplify > > sub-drivers making use of dma coherent helper functions (those drivers > > currently have to explicitly set the dma coherent mask using > > dma_set_coherent_mask function). > > > > Signed-off-by: Boris BREZILLON <[email protected]> > > --- > > > > Hi, > > > > This patch is follow-up of a discussion we had on a KMS driver thread [1]. > > This patch is only copying the parent device coherent_dma_mask to avoid > > calling specific dma_set_coherent_mask in case the coherent mask is the > > default one. > > > > I'm a bit surprised this hasn't been done earlier while other dma fields > > (mask and parms) are already inherited from the parent device, so please > > tell me if there already was an attempt to do the same, and if so, what > > was the reson for rejecting it :-). > > > > > > Seems reasonable to me. It's not clear whether we should always inherit > the dma_mask, but I see no point in copying just dma_mask but not > coherent_dma_mask. I thought about adding a dma_mask field to mfd_cell to override the default behavior (allocate a new dma_mask and copy the value provided by mfd_cell if it's not zero), but I don't see any real use case where a sub-device does not share the dma capabilities with its parent. IMHO, it's safer to keep it as is until someone really need to set a different dma_mask on a sub-device. Best Regards, Boris -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
