On Wed, 2007-03-28 at 00:29 -0600, Eric W. Biederman wrote: > Michael Ellerman <[EMAIL PROTECTED]> writes: > > > The msi descriptors are linked together with what looks a lot like > > a linked list, but isn't a struct list_head list. Make it one. > > > > The only complication is that previously we walked a list of irqs, and > > got the descriptor for each with get_irq_msi(). Now we have a list of > > descriptors and need to get the irq out of it, so it needs to be in the > > actual struct msi_desc. We use 0 to indicate no irq is setup. > > > > At some point after a pci_dev is created we need to initialise its > > msi_list. pci_device_add() looks like the right place to do that, although > > I'm not convinced it's 100% safe. In drivers/char/agp/alpha-agp.c we create > > a pci_dev and I don't see that it ever gets passed to pci_device_add(), but > > we probably don't care. > > Well that one appears to be a dummy place holder and probably should at > least have a kzalloc to initialize all of the fields to know values. > > Regardless the normal pci device allocation does use kzalloc so we will > have well defined if not beautiful behavior if we try and use it. > > Until we have a case where we need to use the msi_list outside of > where we enable and disable msi we should be perfectly fine initializing > the list somewhere inside of pci_enable_msi, and pci_enable_msix. > With dev->msi_enabled and dev->msix_enabled serving as flags to the > rest of the world that it is safe to look at the list. > > It certainly sounds safer to me then becoming to closely coupled with > code that doesn't really care about how msi works. Heck even though > we repeat the call twice I bet it will even be less code.
I thought about doing it in the MSI enable methods, but I think it
really belongs in the (nonexistant) routine that allocs and sets up a
pci_dev.
I think it's pretty dicy to be passing around a pci_dev with an
uninitialised msi_list. Even if currently no code outside the MSI enable
methods looks at it, I think we're asking for bugs in the future.
So I'll do a patch which adds alloc_pci_dev(), update the callers, and
then put the msi_list initialisation in there.
> > --- msi-new.orig/include/linux/msi.h
> > +++ msi-new/include/linux/msi.h
> > @@ -1,6 +1,8 @@
> > #ifndef LINUX_MSI_H
> > #define LINUX_MSI_H
> >
> > +#include <linux/list.h>
> > +
> > struct msi_msg {
> > u32 address_lo; /* low 32 bits of msi message address */
> > u32 address_hi; /* high 32 bits of msi message address */
> > @@ -24,10 +26,8 @@ struct msi_desc {
> > unsigned default_irq; /* default pre-assigned irq */
> > }msi_attrib;
> >
> > - struct {
> > - __u16 head;
> > - __u16 tail;
> > - }link;
> > + int irq;
> This should be "unsigned int irq"
Oops, I'll fix that.
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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