On 05/13/10 02:51 AM, 邓宁 wrote:
Hi all,
Forgive me of the naive questions about PCI device driver.
I am reading something about PCI device driver, as mentioned in the
materials, the PCI device contains three memory space: i/o,
configuration, and memory space.I know that the configuration memory
space is located in the PCI device, which, is responsible for guiding
the allocation of the other two memory spaces. However, I am puzzled
if the two memory spaces(i/o, memory) are really physically existed in
every PCI device, in the form of "an on-device memory"? Or, these
spaces are only allocated at the booting stage and are actually
exitsed in the physical memory range?
In a PCI device driver, I implemented the mmap() function to mmap the
pci device into the user applications, then what's the memory space
mapped? Is it only the "PCI memory space" in the PCI device? Or the
three memory spaces together?
Generally the mmap logic would make just one space available... usually
the system won't allocate contiguous regions to the BARs (base address
registers).
These spaces are generally implemented by the device -- they may take
the form of hardware registers (common), some internal memory mapping,
or some other kind of logic. The PCI spec doesn't say that much about
the details here.
Not every device will have every BAR, either. The only guarantee is that
PCI compliant devices will have configuration space.
Configuration space may or may not be available via directly mapped
memory. Most systems (maybe even all of them) that OpenSolaris supports
use directly mapped memory, but I've seen other systems which use other
mechanisms, such as a pair of indirection registers, to access PCI
configuration space. So its important that you use the DDI provided for
these kinds of access (pci_config_setup, etc.)
- Garrett
_______________________________________________
driver-discuss mailing list
driver-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/driver-discuss
