Re: [LTP] [PATCH] device-drivers: pci: fix PCI_EXP_CAP_CONFIG test-case

[alexey.kodanev@oracle.com]

Hi!
On 10/31/2013 05:38 AM, Wanlong Gao wrote:
> On 10/30/2013 07:21 PM, Alexey Kodanev wrote:
>> There is another way to check that PCI Express config space of pci devices
>> can be read successfully.
>> Firstly, find out if a device has a PCI Express Capability: we should get
>> a correct config address offset from the dev's structure (dev->pcie_cap).
>> Using the offset, read a PCI Express header. Check if we can get the right
>> PCI Express CAP ID from the header (it must match the PCI_CAP_ID_EXP macro).
> This can PASS here, thank you.
>
> Why did the original method always FAIL?

The original code has wrong offset, should be reg = 0x100 at least (as 
it written in comment):
> int reg = 100, len = 4; /*PCI-Exp enhanced config register 0x100, 4 
> implies dword access */

I don't know about that magic number 0x14011 in the original code. 
Comments said that we can find a constant value from that offset, but in 
truth, we can find any of the PCI_EXT_CAP_ID_* macors in the first 16 
bits or none if device doesn't have Extended Configuration Space. It can 
be AER (ERR in the macro) and it could be any other ID (it depends on 
the device).

better find a particular offset using the kernel function, for example:
pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR); /* it will find 
Advanced Error Reporting structure */

Then get the header (first 4 bytes). First 16 bits should be AER_ID, 
that it is to say 0x0001. From bit 16 to bit 19 - capability version 
(can be 1h or 2h). The other bits contain the offset to the next PCI 
Express Capability structure or zero if it is the last one. That kind of 
header will never equal to 0x14011, that's is why the original method 
will always fail even with the right offset.


------------------------------------------------------------------------------
Android is increasing in popularity, but the open development platform that
developers love is also attractive to malware creators. Download this white
paper to learn more about secure code signing practices that can help keep
Android apps secure.
http://pubads.g.doubleclick.net/gampad/clk?id=65839951&iu=/4140/ostg.clktrk
_______________________________________________
Ltp-list mailing list
Ltp-list@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/ltp-list