linux-kernel - Re: [RFC PATCH v4 3/5] PCI: Check platform specific ECAM quirks

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Date:	Tue, 28 Jun 2016 09:04:42 -0400
From:	Christopher Covington <cov@...eaurora.org>
To:	Tomasz Nowicki <tn@...ihalf.com>, helgaas@...nel.org,
	arnd@...db.de, will.deacon@....com, catalin.marinas@....com,
	rafael@...nel.org, hanjun.guo@...aro.org,
	Lorenzo.Pieralisi@....com, okaya@...eaurora.org,
	jchandra@...adcom.com
Cc:	robert.richter@...iumnetworks.com, mw@...ihalf.com,
	Liviu.Dudau@....com, ddaney@...iumnetworks.com,
	wangyijing@...wei.com, msalter@...hat.com,
	linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linaro-acpi@...ts.linaro.org, jcm@...hat.com,
	andrea.gallo@...aro.org, dhdang@....com, jeremy.linton@....com,
	liudongdong3@...wei.com, gabriele.paoloni@...wei.com,
	jhugo@...eaurora.org, Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [RFC PATCH v4 3/5] PCI: Check platform specific ECAM quirks

Hi Tomasz,

On 06/28/2016 03:54 AM, Tomasz Nowicki wrote:

> diff --git a/drivers/pci/host/mcfg-quirks.c b/drivers/pci/host/mcfg-quirks.c
> new file mode 100644
> index 0000000..fb2b184
> --- /dev/null
> +++ b/drivers/pci/host/mcfg-quirks.c
> @@ -0,0 +1,88 @@

> +static bool pci_mcfg_fixup_match(struct pci_cfg_fixup *f,
> +				 struct acpi_table_header *mcfg_header)
> +{
> +	int olen = min_t(u8, strlen(f->oem_id), ACPI_OEM_ID_SIZE);
> +	int tlen = min_t(u8, strlen(f->oem_table_id), ACPI_OEM_TABLE_ID_SIZE);
> +
> +	return (!strncmp(f->oem_id, mcfg_header->oem_id, olen) &&
> +		!strncmp(f->oem_table_id, mcfg_header->oem_table_id, tlen) &&
> +		f->oem_revision == mcfg_header->oem_revision);
> +}

Ard's comments on v3 included:

"... exact OEM table/rev id matches ..."
"... substring match ... out of the question ..."

I originally advocated the substring match approach because
space-padding the input strings was unfamiliar. But given that some
vendors have a "PLAT    " then "PLAT2   " naming scheme, where the
former needs quirks and the latter (hopefully) doesn't, I agree with Ard
and think space-padded inputs is the better way to go. Sorry for the
lack of foresight.

(I'm happy to rip it out, test, and communicate the delta however you'd
prefer--just let me know.)

Regards,
Cov

-- 
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