On Thu, Mar 21, 2019 at 03:52:28PM -0700, Christoph Hellwig wrote: > We still have a few drivers which pass a NULL struct device pointer > to DMA API functions, which generally is a bad idea as the API > implementations rely on the device not only for ops selection, but > also the dma mask and various other attributes, and many implementations > have been broken for NULL device support for a while. I think I must be missing something, but... My understanding is that ISA DMA is normally limited to 24 bits of address - indeed, the x86 version only programs 24 bits of DMA address. Looking through this series, it appears that the conversions mean that the DMA mask for ISA becomes the full all-ones DMA mask, which would of course lead to memory corruption if only 24 bits of the address end up being programmed into the hardware. Maybe you could say why you think this series is safe in regard to ISA DMA? > > This series removes the few remaning users that weren't picked up in > the last merge window and then removes core support for this "feature". > > A git tree is also available at: > > git://git.infradead.org/users/hch/misc.git dma-remove-NULL-dev-support > > Gitweb: > > http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dma-remove-NULL-dev-support > -- RMK's Patch system: https://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
