From mboxrd@z Thu Jan  1 00:00:00 1970
From: tn@semihalf.com (Tomasz Nowicki)
Date: Tue, 19 Jan 2016 08:55:21 +0100
Subject: [PATCH V3 20/21] pci, acpi: Match PCI config space accessors
 against platfrom specific quirks.
In-Reply-To: <569D9634.3040304@huawei.com>
References: <1452691267-32240-1-git-send-email-tn@semihalf.com>
 <1452691267-32240-21-git-send-email-tn@semihalf.com>
 <1452785776.28109.22.camel@redhat.com> <569CDD8F.807@semihalf.com>
 <569D9634.3040304@huawei.com>
Message-ID: <569DEBE9.5090909@semihalf.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 19.01.2016 02:49, liudongdong (C) wrote:
> Hi Tomasz, Mark
>
> ? 2016/1/18 20:41, Tomasz Nowicki ??:
>> On 14.01.2016 16:36, Mark Salter wrote:
>>>> +extern struct pci_mcfg_fixup __start_acpi_mcfg_fixups[];
>>>> >+extern struct pci_mcfg_fixup __end_acpi_mcfg_fixups[];
>>>> >+
>>>> >+static struct pci_ops *pci_mcfg_check_quirks(struct acpi_pci_root
>>>> *root)
>>>> >+{
>>>> >+    struct pci_mcfg_fixup *f;
>>>> >+    int bus_num = root->secondary.start;
>>>> >+    int domain = root->segment;
>>>> >+
>>>> >+    /*
>>>> >+     * First match against PCI topology <domain:bus> then use DMI or
>>>> >+     * custom match handler.
>>>> >+     */
>>>> >+    for (f = __start_acpi_mcfg_fixups; f < __end_acpi_mcfg_fixups;
>>>> f++) {
>>>> >+        if ((f->domain == domain || f->domain ==
>>>> PCI_MCFG_DOMAIN_ANY) &&
>>>> >+            (f->bus_num == bus_num || f->bus_num ==
>>>> PCI_MCFG_BUS_ANY) &&
>>>> >+            (f->system ? dmi_check_system(f->system) : 0 ||
>>>> >+             f->match ? f->match(f, root) : 0))
>>>> >+            return f->ops;
>>> I think this would be better as:
>>>
>>>             (f->system ? dmi_check_system(f->system) : 1 &&
>>>              f->match ? f->match(f, root) : 1))
>>>             return f->ops;
>>>
>>> Otherwise, one has to call dmi_check_system() from f->match() if
>>> access to root is needed.
>>
>
> Non-DMI, we need not to call dmi_check_system() from f->match(),
> we can use _HID to decide to hook the pci_ops or not.

Sorry, but I dont understand your point. Can you elaborate?

With Mark modification, you can use the following cases to identify 
platform:
1. DMI only
2. f->match() only (_HID can be used there)
3. DMI and f->match()

DMI used to be very convenient way to recognise platform, sometimes it 
is not enough, hence f->match() alternative.

Tomasz