On 29.06.16 15:56:50, Ard Biesheuvel wrote:
On 29 June 2016 at 15:34, Christopher Covington cov@codeaurora.org wrote:
Hi Tomasz,
On 06/29/2016 06:48 AM, Tomasz Nowicki wrote:
On 28.06.2016 18:12, Duc Dang wrote:
On Tue, Jun 28, 2016 at 6:04 AM, Christopher Covington cov@codeaurora.org wrote:
Hi Tomasz,
Ard's comments on v3 included:
"... exact OEM table/rev id matches ..." "... substring match ... out of the question ..."
Digging through the archives I see Jon Master commented earlier to "be careful with substring match".
I think having OEM Table ID as "PLAT " and then "PLAT2 " (the the next version of the SoC) is common. So yes, matching full string is better as we can use "PLAT2 " in MCFG table and not worry about the "PLAT" sub-string match causes the quirk to be applied unintentionally.
Note that platforms already shipped where OEM string has no padding will
I'm confused by this statement. OEMID is defined as 6 bytes long and OEM Table ID as 8 bytes long in the ACPI specification. As far as I can tell, if your string isn't exactly that long, padding up to that length is required.
have change the firmware or add 0 padding to our quirk array IDs.
The fixed 6 or 8 character string compare, as used v2 of this patchset, will be compatible with existing firmware as best I can tell. Adding padding to the quirk array IDs is exactly what I'm suggesting, although all the strings I've seen are space padded rather than null padded.
I don't think any interpretation of the 6 or 8 byte wide OEM fields is necessary to be able to match it against a list of known values as used by the quirky platforms. We need an exact match against whatever we know is in the table of an affected system, and whether a space qualifies as padding or as a character is irrelevant.
Matches: {"APM ", "XGENE ", 1} {"CAVIUM", "THUNDERX", 1} {"HISI ", "HISI-D02", 1} {"HISI ", "HISI-D03", 1} {"QCOM ", "QDF2432 ", 1}
I would not mind listing these as
{ { 'A','P','M',' ',' ',' ',' '}, {'X','G','E','N','E',' ',' ',' '}, 1} ...
just to stress that we are not dealing with C strings (and to avoid having to deal with the implicit NUL terminator). That also means memcmp() with a fixed length is the most appropriate to perform the comparison
I still would go with memcmp but have the char arrays null terminated in addition. This first makes string handling easier, and fixes some unterminated %s printfs bugs in the code.
Thus, I would prefer to go with:
struct pci_cfg_fixup { char oem_id[ACPI_OEM_ID_SIZE + 1]; char oem_table_id[ACPI_OEM_TABLE_ID_SIZE + 1]; ...
static struct pci_cfg_quirks mcfg_qurks[] __initconst = { /* { OEM_ID, OEM_TABLE_ID, REV, DOMAIN, BUS_RANGE, pci_ops, init_hook }, */ #ifdef CONFIG_PCI_HOST_THUNDER_PEM /* Pass2.0 */ { "CAVIUM", "THUNDERX", 1, ...
This is also no "pain in the eyes". :)
If there are zero bytes in then just use \0, e.g.:
{ "foo\0\0\0", "foobar\0\0", ... }
For comparisation still use memcmp accordingly:
memcmp(..., ACPI_OEM_ID_SIZE); memcmp(..., ACPI_OEM_TABLE_ID_SIZE);
The following would be fixed too as strings are now null terminated:
pr_info("Handling %s %s r%d PCI MCFG quirks\n", f->oem_id, f->oem_table_id, f->oem_revision);
Btw, use dev_info(&root->device->dev, ...) here for pr_info() and modify message text, e.g.:
acpi PNP0A08:04: Applying PCI MCFG quirks for CAVIUM THUNDERX rev: 1
And, we should support some sort of MCFG_OEM_REVISION_ANY to move the rev handling optional to pci_cfg_fixup::init().
Plus one spelling fix: mcfg_qurks -> mcfg_quirks
Thanks,
-Robert
Given the above tuples, won't accidentally match: (guessing at possible future ids) {"APM ", "XGENEi ", 1} {"CAVIUM", "THUNDERX", i} i != 1 {"CAVIUM", "THUNDERi", 1} {"CAVIUM", "THUNDRXi", 1} {"HISI ", "HISI-D0i", 1} i != 2 && i != 3 {"QCOM ", "QDF24ij ", 1} i != 3 && j != 2
References for APM, HiSilicon IDs: https://lists.linaro.org/pipermail/linaro-acpi/2016-June/007108.html https://lists.linaro.org/pipermail/linaro-acpi/2016-June/007043.html
Thanks, Cov
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