On 2013-04-10 17:16, H Hartley Sweeten wrote:
On Wednesday, March 06, 2013 4:34 PM, H Hartley Sweeten wrote:
Question, when doing an ioremap() of a PCI resource which is more correct?
iobase = pci_resource_start(pcidev, bar);
len = pci_resource_len(pcidev, bar);
mmio = ioremap(iobase, len);
or
mmio = pci_ioremap_bar(pcidev, bar);
pci_ioremap_bar() does some extra sanity checking to make sure the bar
is actually a memory resource and then does an ioremap_nocache().
If the ioremap() is in order to talk to the registers on the PCI device wouldn't
the pci_ioremap_bar() be more correct?
Greg / Ian / Dan,
Do you have any ideas/opinions on the question above?
Saves a couple of lines of code, I suppose. The extra sanity makes
sense for the function to do for defensive programming reasons, but is
not particularly useful for the caller unless there are some (presumably
older) variants of a PCI card that match the driver's PCI ID table, but
have registers in I/O space instead of memory space (in which case, it's
better that pci_ioremap_bar() returns the NULL rather than
ioremap_nocache() attempting to remap a port address (though that would
probably fail and return NULL anyway).
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-
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