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Subject: Re: [PATCH v14 1/9] LIB: Introduce a generic PIO mapping method
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
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From:   John Garry <john.garry@huawei.com>
Message-ID: <7197ce31-c4c2-d00e-be04-1edc14c3e721@huawei.com>
Date:   Tue, 20 Feb 2018 15:06:51 +0000
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On 20/02/2018 14:33, Andy Shevchenko wrote:
> On Mon, Feb 19, 2018 at 7:48 PM, John Garry <john.garry@huawei.com> wrote:
>> From: Zhichang Yuan <yuanzhichang@hisilicon.com>
>>
>> In commit 41f8bba7f555 ("of/pci: Add pci_register_io_range() and
>> pci_pio_to_address()"), a new I/O space management was supported. With
>> that driver, the I/O ranges configured for PCI/PCIe hosts on some
>> architectures can be mapped to logical PIO, converted easily between
>> CPU address and the corresponding logicial PIO. Based on this, PCI
>> I/O devices can be accessed in a memory read/write way through the
>> unified in/out accessors.
>>
>> But on some archs/platforms, there are bus hosts which access I/O
>> peripherals with host-local I/O port addresses rather than memory
>> addresses after memory-mapped.
>>
>> To support those devices, a more generic I/O mapping method is introduced
>> here. Through this patch, both the CPU addresses and the host-local port
>> can be mapped into the logical PIO space with different logical/fake PIOs.
>> After this, all the I/O accesses to either PCI MMIO devices or host-local
>> I/O peripherals can be unified into the existing I/O accessors defined in
>> asm-generic/io.h and be redirected to the right device-specific hooks
>> based on the input logical PIO.
>

Hi Andy,

>> +#define PIO_INDIRECT           0x01UL /* indirect IO flag */
>> +#define PIO_CPU_MMIO           0x00UL /* memory mapped io flag */
>
> It looks like bitfield, but from use I don't see it.
>

IIRC, the orignal intention was that this would be a bit value in a 
bitfield.

> Perhaps use enum instead?

I'll change to enum to be clear.

>> +       resource_size_t hwaddr = -1;
>
>> +unsigned long
>> +               return -1;
>> +               return -1;
>
>> +unsigned long
>> +       return -1;
>
>> +type logic_in##bw(unsigned long addr)                                  \
>> +       type ret = -1;                                                  \
>
> All types above are unsigned. I'm not sure it's the best approach to
> use -1 implicitly casted to unsigned type.
>
> I would rather use ~0UL or alike.
>

Yes, I can change these.

Much appreciated,
John