Re: [Linaro-mm-sig] [RFCv2 2/2] dma-buf: add helpers for sharing attacher constraints with dma-parms

On Wed, Jan 21, 2015 at 09:46:47AM +0530, Sumit Semwal wrote:

+static int calc_constraints(struct device *dev,

• 	    struct dma_buf_constraints *calc_cons)
  

+{

• struct dma_buf_constraints cons = *calc_cons;
• cons.dma_mask &= dma_get_mask(dev);

I don't think this makes much sense when you consider that the DMA infrastructure supports buses with offsets. The DMA mask is th upper limit of the _bus_ specific address, it is not a mask per-se.

What this means is that &= is not the right operation. Moreover, simply comparing masks which could be from devices on unrelated buses doesn't make sense either.

However, that said, I don't have an answer for what you want to achieve here.