On Wed, 2024-01-17 at 10:59 +0100, Philipp Stanner wrote: > On Tue, 2024-01-16 at 23:17 +0200, andy.shevchenko@xxxxxxxxx wrote: > > Mon, Jan 15, 2024 at 03:46:11PM +0100, Philipp Stanner kirjoitti: [...] > > > > > > > PCI's devres API suffers several weaknesses: > > > > > > 1. There are functions prefixed with pcim_. Those are always > > > managed > > > counterparts to never-managed functions prefixed with pci_ – > > > or > > > so one > > > would like to think. There are some apparently unmanaged > > > functions > > > (all region-request / release functions, and pci_intx()) which > > > suddenly become managed once the user has initialized the > > > device > > > with > > > pcim_enable_device() instead of pci_enable_device(). This > > > "sometimes > > > yes, sometimes no" nature of those functions is confusing and > > > therefore bug-provoking. In fact, it has already caused a bug > > > in > > > DRM. > > > The last patch in this series fixes that bug. > > > 2. iomappings: Instead of giving each mapping its own callback, > > > the > > > existing API uses a statically allocated struct tracking one > > > mapping > > > per bar. This is not extensible. Especially, you can't create > > > _ranged_ managed mappings that way, which many drivers want. > > > 3. Managed request functions only exist as "plural versions" with > > > a > > > bit-mask as a parameter. That's quite over-engineered > > > considering > > > that each user only ever mapps one, maybe two bars. > > > > > > This series: > > > - add a set of new "singular" devres functions that use devres > > > the > > > way > > > its intended, with one callback per resource. > > > - deprecates the existing iomap-table mechanism. > > > - deprecates the hybrid nature of pci_ functions. > > > - preserves backwards compatibility so that drivers using the > > > existing > > > API won't notice any changes. > > > - adds documentation, especially some warning users about the > > > complicated nature of PCI's devres. > > > > Instead of adding pcim_intx(), please provide proper one for > > pci_alloc_irq_vectors(). Ideally it would be nice to deprecate > > old IRQ management functions in PCI core and delete them in the > > future. > > > > In order to deprecate the intermingling with half-managed hyprid > devres > in pci.c, you need to have pci_intx() be backwards compatible. Unless > you can remove it at once. > And the least broken way to do that I thought would be pcim_intx(), > because that's consistent with how I make pci_request_region() & Co. > call into their managed counterparts. > > There are 25 users of pci_intx(). > We'd have to look how many of them call pcim_enable_device() and how > easy they would be to port to... pci_alloc_irq_vectors() you say? I > haven't used that before. Would have to look into it and see how we > could do that. Alright, so I thought about that a bit. So pci_intx() is the old way to do it and you would like to deprecate it for good. Understood, makes sense This series, however, is about deprecating PCI's broken devres implementation – not about deprecating outdated PCI features in general. So I wouldn't like to touch anything here unless cleaning up devres demands it. Now the question would be: how can we solve this? My suggestion would be: Let's implement pcim_intx(), but only make it visible through drivers/pci/pci.h. So we won't make it usable for other drivers, don't EXPORT_SYMBOL() it and basically only have it as a tool to move the devres-part clearly and cleanly from pci.c to devres.c Further deprecating old PCI stuff could then be done in a separate series. ACK? P. > > > P.
