On Wed, Nov 28, 2018 at 08:47:05AM -0800, Linus Torvalds wrote: > On Tue, Nov 27, 2018 at 11:41 PM Christoph Hellwig <hch@xxxxxx> wrote: > > > > On Fri, Nov 23, 2018 at 07:55:11AM +0100, Christoph Hellwig wrote: > > > Well, I can tweak the last patch to return -EINVAL from dma_mapping_error > > > instead of the old 1 is as bool true. The callers should all be fine, > > > although I'd have to audit them. Still wouldn't help with being able to > > > return different errors. > > > > Any opinions? I'd really like to make some forward progress on this > > series. > > So I do think that yes, dma_mapping_error() should return an error > code, not 0/1. > > But I was really hoping that the individual drivers themselves could > return error codes. Right now the patch-series has code like this: > > ret = needs_bounce(dev, dma_addr, size); > if (ret < 0) > - return ARM_MAPPING_ERROR; > + return DMA_MAPPING_ERROR; > > which while it all makes sense in the context of this patch-series, I > *really* think it would have been so much nicer to return the error > code 'ret' instead (which in this case is -E2BIG). > > I don't think this is a huge deal, but ERR_PTR() has been hugely > successful elsewhere. And I'm not hugely convinced about all these > "any address can be valid" arguments. How the hell do you generate a > random dma address in the last page that isn't even page-aligned? kmalloc() a 64-byte buffer, dma_map_single() that buffer. If you have RAM that maps to a _bus_ address in the top page of 4GB of a 32-bit bus address, then you lose. Simples. Subsystems like I2C, SPI, USB etc all deal with small kmalloc'd buffers and their drivers make use of DMA. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up
