Re: [PATCH 1/2] [RFC] PCI: read revision ID by default

[Kok, Auke]

Grant Grundler wrote:
> On Fri, Jun 08, 2007 at 03:46:30PM -0700, Auke Kok wrote:
> > Currently there are 97 occurrences where drivers need the pci
> > revision ID. We can do this once for all devices. Even the pci
> > subsystem needs the revision several times for quirks. The extra
> > u8 member pads out nicely in the pci_dev struct.
>
> Good idea. I always wondered why we read the invariants so often
> in the code.
>
> > Signed-off-by: Auke Kok <auke-jan.h.kok@xxxxxxxxx>
> > ---
> >
> >  drivers/pci/probe.c |    3 +++
> >  include/linux/pci.h |    1 +
> >  2 files changed, 4 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index e48fcf0..0fdb71d 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -918,6 +918,9 @@ pci_scan_device(struct pci_bus *bus, int devfn)
> >  	dev->cfg_size = pci_cfg_space_size(dev);
> >  	dev->error_state = pci_channel_io_normal;
> >  
> > +	/* read the PCI revision: 1 byte */
> > +	pci_read_config_byte(dev, PCI_REVISION_ID, &dev->revision);
>
> probe.c:pci_setup_device() is also reading this byte but discards it:
> 	pci_read_config_dword(dev, PCI_CLASS_REVISION, &class);
> 	class >>= 8;                                /* upper 3 bytes */
> 	dev->class = class;
>
> Can you use "class & 0xff"? Or is pci_setup_device() too late?
> Or can you read the whole 32-bits in pci_scan_device() and remove
> the pci_read_config() in pci_setup_device()?

no, pci_setup_device() is just called right after the location where I read the 
REVISION_ID. I'll remove the read and put the dev->revision right after where we 
read the class dword.

Auke
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