linux-kernel - Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports

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Date:	Wed, 23 Dec 2015 17:04:40 +0530
From:	Santosh Shukla <santosh.shukla@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"H. Peter Anvin" <hpa@...or.com>, josh@...htriplett.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	akpm@...ux-foundation.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-api@...r.kernel.org, yuanhan.liu@...ux.intel.com
Subject: Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit
 and 32-bit ports

On 23 December 2015 at 03:26, Arnd Bergmann <arnd@...db.de> wrote:
> On Tuesday 22 December 2015, Santosh Shukla wrote:
>> }
>>
>> So I care for /dev/ioport types interface who could do more than byte
>> data copy to/from user-space. I tested this patch with little
>> modification and could able to run pmd driver for arm/arm64 case.
>>
>> Like to know how to address pci_io region mapping problem for
>> arm/arm64, in-case /dev/ioports approach is not acceptable or else I
>> can spent time on restructuring the patch?
>>
>
> For the use case you describe, can't you use the vfio framework to
> access the PCI BARs?
>

I looked at file: drivers/vfio/pci/vfio_pci.c, func vfio_pci_map() and
it look to me that it only maps ioresource_mem pci region, pasting
code snap:

if (!(pci_resource_flags(pdev, index) & IORESOURCE_MEM))
return -EINVAL;
....

and I want to map ioresource_io pci region for arm platform in my
use-case. Not sure vfio maps pci_iobar region?

> After all, you are talking about regular PCI devices, not access to
> random unknown I/O port numbers.
>
Yes, pci_iobar region.

>         Arnd
> --
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