On Tue, 2007-03-27 at 23:54 -0600, Eric W. Biederman wrote: > Michael Ellerman <[EMAIL PROTECTED]> writes: > > > Add an arch_msi_supported(), which gives archs a chance to check the input > > to pci_enable_msi/x. For MSI-X this routine might need the entry array, so > > pass it in. For plain MSI, NULL is passed, the arch routine needs to cope > > with that. Propagate the error value returned from the arch routine out to > > the caller. > > Ugh. I'm not very comfortable with passing struct msix_entry into > the architectures right now. > > There are a couple of reasons. > - It's irq field is to small (so we need to change it at some point) > - No a single driver that calls pci_enable_msix uses the scatter gather > feature (so the entry member is redundant). > > So this struct msix_entry needs to change and we need to change the drivers > along with it. Having to change a couple of architectures as well sounds > painful. So we might as well fix that at the same time as we are > adding the RTAS support so architectures don't have to deal with this > nasty unused concept. > > I'm thinking the same thing to do is to completely remove struct msix_entry > and just let drivers walk the linked list you introduce a few patches > later down. All they need is to get their irq numbers anyway.
I agree with most of that. I thought of doing that change, but didn't want to have the powerpc code stuck behind a huge pile of driver changes. My only other worry is that at some point we'll get a driver that does want to choose the entries it's allocated, and at that point we'll have to put back the msix_entry code (or something similar). I don't have any idea of when/if that sort of hardware/driver requirement is likely to surface though, if it's "not for a while" it might be worth ripping out the complexity until we really need it. > I was tempted to drop nvec as well since our irq numbers are virtual, > we could always delay the failure into request_irq. But there are > a few embedded architectures like the arm where the number irqs > numbers may stay limited for a long time and if the driver will never > use all of the irqs we get to save some resources and some work. So > that makes sense. I think nvec should stay. > So can we please at least move this patch down to the end with the > rest of the RTAS arch support? > > Moving it towards the end will allow it to be reviewed in the context > where it will be used and it will give us a chance to simplify > pci_enable_msix before we get there. I'm happy to move it to the end of the series. I'm also happy to stop passing the msix_entry into the arch. But I don't want to predicate the merge of our powerpc stuff on the removal of msix_entry entirely, there's too much risk that we'll slip to v23. cheers -- Michael Ellerman OzLabs, IBM Australia Development Lab wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183) We do not inherit the earth from our ancestors, we borrow it from our children. - S.M.A.R.T Person
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