linux-kernel - Re: [PATCH v5 2/6] uio: Add new UIO_MEM_PHYS

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Message-ID: <CAPTm99WWk6XZnEjwjiDoxxGZdR6WccFXZBAjOfpWNq1dWrBfjw@mail.gmail.com>
Date:	Mon, 8 Dec 2014 18:13:28 +0530
From:	Ankit Jindal <ankit.jindal@...aro.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Hans J. Koch" <hjk@...sjkoch.de>,
	"patches@....com" <patches@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Rob Herring <robh+dt@...nel.org>,
	Tushar Jagad <tushar.jagad@...aro.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Varka Bhadram <varkabhadram@...il.com>,
	Kumar Gala <galak@...eaurora.org>,
	Anup Patel <anup@...infault.org>,
	Andreas Färber <afaerber@...e.de>
Subject: Re: [PATCH v5 2/6] uio: Add new UIO_MEM_PHYS_CACHE type for mem regions

On 27 November 2014 at 05:31, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Mon, Nov 17, 2014 at 04:06:08PM +0530, Ankit Jindal wrote:
>> Currently, three types of mem regions are supported: UIO_MEM_PHYS,
>> UIO_MEM_LOGICAL and UIO_MEM_VIRTUAL. Among these UIO_MEM_PHYS helps
>> UIO driver export physcial memory to user space as non-cacheable
>> user memory. Typcially memory-mapped registers of a device are exported
>> to user space as UIO_MEM_PHYS type mem region. The UIO_MEM_PHYS type
>> is not efficient if dma-capable devices are capable of maintaining coherency
>> with CPU caches.
>
> Not efficient in what way?
Sorry, I will rephrase this.
>
>> This patch adds new type UIO_MEM_PHYS_CACHE for mem regions to enable
>> cacheable access to physical memory from user space.
>>
>> Signed-off-by: Ankit Jindal <ankit.jindal@...aro.org>
>> Signed-off-by: Tushar Jagad <tushar.jagad@...aro.org>
>> ---
>>  drivers/uio/uio.c          |   11 ++++++++---
>>  include/linux/uio_driver.h |    1 +
>>  2 files changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
>> index 97e6444..120a84b 100644
>> --- a/drivers/uio/uio.c
>> +++ b/drivers/uio/uio.c
>> @@ -644,7 +644,7 @@ static const struct vm_operations_struct uio_physical_vm_ops = {
>>  #endif
>>  };
>>
>> -static int uio_mmap_physical(struct vm_area_struct *vma)
>> +static int uio_mmap_physical(struct vm_area_struct *vma, bool cacheable)
>
> I despise "bool" flags in a function, as they don't give any idea of
> what is going on when you see the function being called.  Please create
> a new function that does this properly, with a correct name, if it's
> needed.
Sure, will take care of this in next revision.
>
> thanks,
>
> greg k-h
Thanks,
Ankit
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