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From: "Luis R. Rodriguez" <mcgrof@do-not-panic.com>
Date: Thu, 25 Jun 2015 08:53:35 -0700
Message-ID: <CAB=NE6XJUwBg46tNOt=Y9zpuM8jZbeV-G_ndTQCC0+uO=wOgzw@mail.gmail.com>
Subject: Re: [PATCH v8 5/9] PCI: Add pci_iomap_wc() variants
To: Borislav Petkov <bp@suse.de>
Cc: Ingo Molnar <mingo@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Tomi Valkeinen <tomi.valkeinen@ti.com>,
        "Michael S. Tsirkin" <mst@redhat.com>, Toshi Kani <toshi.kani@hp.com>,
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        Suresh Siddha <sbsiddha@gmail.com>, Ingo Molnar <mingo@elte.hu>,
        Thomas Gleixner <tglx@linutronix.de>, Juergen Gross <jgross@suse.com>,
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On Thu, Jun 25, 2015 at 8:09 AM, Borislav Petkov <bp@suse.de> wrote:
>> +void __iomem *pci_iomap_wc_range(struct pci_dev *dev,
>> +                              int bar,
>> +                              unsigned long offset,
>> +                              unsigned long maxlen)
>> +{
>> +     resource_size_t start = pci_resource_start(dev, bar);
>> +     resource_size_t len = pci_resource_len(dev, bar);
>> +     unsigned long flags = pci_resource_flags(dev, bar);
>> +
>> +     if (len <= offset || !start)
>> +             return NULL;
>> +     len -= offset;
>> +     start += offset;
>> +     if (maxlen && len > maxlen)
>> +             len = maxlen;
>> +     if (flags & IORESOURCE_IO)
>> +             return NULL;
>
> I've moved this check at the beginning of the function so that we bail
> out before doing the computations above it.

That indeed looks like a good optimization.

 Luis
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