linux-kernel - Re: [PATCH 2/4] PCI: add functionality for resizing resources v3

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Date:   Tue, 2 May 2017 17:51:36 +0200
From:   Christian König <deathsimple@...afone.de>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     helgaas@...nel.org,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] PCI: add functionality for resizing resources v3

Am 26.04.2017 um 19:00 schrieb Andy Shevchenko:
> On Tue, Apr 25, 2017 at 4:19 PM, Christian König
> <deathsimple@...afone.de> wrote:
>> From: Christian König <christian.koenig@....com>
>>
>> This allows device drivers to request resizing their BARs.
>>
>> The function only tries to reprogram the windows of the bridge directly above
>> the requesting device and only the BAR of the same type (usually mem, 64bit,
>> prefetchable). This is done to make sure not to disturb other drivers by
>> changing the BARs of their devices.
>>
>> If reprogramming the bridge BAR fails the old status is restored and -ENOSPC
>> returned to the calling device driver.
>> +int pci_reassign_bridge_resources(struct pci_dev *bridge, unsigned long type)
>> +{
>> +       const unsigned long type_mask = IORESOURCE_IO | IORESOURCE_MEM |
>> +               IORESOURCE_PREFETCH | IORESOURCE_MEM_64;
>> +
> Redundant.

Redundant, but also a reminder to myself that I wanted to ask something 
about that.

This type_mask is used already three times in this file, shouldn't we 
add a define for that?

> [SNIP]
>> +       list_for_each_entry(dev_res, &saved, list) {
>> +               /* Skip the bridge we just assigned resources for. */
>> +               if (bridge == dev_res->dev)
>> +                       continue;
>> +
>> +               bridge = dev_res->dev;
>> +               pci_setup_bridge(bridge->subordinate);
>> +       }
>> +
>> +       free_list(&saved);
>> +       free_list(&failed);
>> +       return ret;
> You might re-use two lines with below, but perhaps better to show
> which case returns 0 explicitly and drop assignment ret = 0 above.

Good point, but actually the free_list(&failed) is superfluous here 
since when the failed list isn't empty we end up in the cleanup path.

Going to fix all other comments in the next version.

Regards,
Christian.