linux-kernel - Re: [PATCH v2 13/13] tty: pruss SUART driver

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Message-ID: <6E7634AAF813458489E0444DF71260CF@subhasishg>
Date:	Wed, 23 Feb 2011 19:05:53 +0530
From:	"Subhasish Ghosh" <subhasish@...tralsolutions.com>
To:	"Greg KH" <gregkh@...e.de>, "Alan Cox" <alan@...rguk.ukuu.org.uk>
Cc:	"Arnd Bergmann" <arnd@...db.de>,
	<linux-arm-kernel@...ts.infradead.org>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	<sachi@...tralsolutions.com>,
	<davinci-linux-open-source@...ux.davincidsp.com>, <nsekhar@...com>,
	"open list" <linux-kernel@...r.kernel.org>, <m-watkins@...com>,
	"Stalin Srinivasan" <stalin.s@...tralsolutions.com>
Subject: Re: [PATCH v2 13/13] tty: pruss SUART driver

Hello,

Anything regarding this.

--------------------------------------------------
From: "Subhasish Ghosh" <subhasish@...tralsolutions.com>
Sent: Wednesday, February 23, 2011 11:00 AM
To: "Greg KH" <gregkh@...e.de>; "Alan Cox" <alan@...rguk.ukuu.org.uk>
Cc: "Arnd Bergmann" <arnd@...db.de>; <linux-arm-kernel@...ts.infradead.org>; 
"Thomas Gleixner" <tglx@...utronix.de>; <sachi@...tralsolutions.com>; 
<davinci-linux-open-source@...ux.davincidsp.com>; <nsekhar@...com>; "open 
list" <linux-kernel@...r.kernel.org>; <m-watkins@...com>; "Stalin 
Srinivasan" <stalin.s@...tralsolutions.com>
Subject: Re: [PATCH v2 13/13] tty: pruss SUART driver

> I could not follow the recommendations clearly.
> This is just to clarify.
>
> Currently, I have the following files for the suart implementation:
>
> drivers/tty/serial/da8xx_pruss/pruss_suart_api.h
> drivers/tty/serial/da8xx_pruss/pruss_suart_err.h
> drivers/tty/serial/da8xx_pruss/pruss_suart_regs.h
> drivers/tty/serial/da8xx_pruss/pruss_suart_board.h
> drivers/tty/serial/da8xx_pruss/pruss_suart_mcasp.h
> drivers/tty/serial/da8xx_pruss/pruss_suart_utils.h
>
> drivers/tty/serial/da8xx_pruss/pruss_suart_api.c
> drivers/tty/serial/da8xx_pruss/pruss_suart.c
> drivers/tty/serial/da8xx_pruss/pruss_suart_utils.c
>
> Of these, I will be removing pruss_suart_err.h as part of the Linux error 
> code cleanup.
> But, I need to keep at least  pruss_suart_board.h as a separate file, as 
> this defines
> configurations which will be often modified by users, I don't want to mix 
> it with other files.
>
> Should I combine rest of the headers into a single file ? and keep the 
> other three .c files under "drivers/tty/serial/"
> and remove the da8xx_pruss directory altogether.
>
>
> --------------------------------------------------
> From: "Greg KH" <gregkh@...e.de>
> Sent: Tuesday, February 22, 2011 8:07 PM
> To: "Subhasish Ghosh" <subhasish@...tralsolutions.com>
> Cc: "Arnd Bergmann" <arnd@...db.de>; 
> <linux-arm-kernel@...ts.infradead.org>; "Thomas Gleixner" 
> <tglx@...utronix.de>; "Alan Cox" <alan@...rguk.ukuu.org.uk>; 
> <sachi@...tralsolutions.com>; 
> <davinci-linux-open-source@...ux.davincidsp.com>; <nsekhar@...com>; "open 
> list" <linux-kernel@...r.kernel.org>; <m-watkins@...com>
> Subject: Re: [PATCH v2 13/13] tty: pruss SUART driver
>
>> On Tue, Feb 22, 2011 at 02:12:32PM +0530, Subhasish Ghosh wrote:
>>> Hello,
>>>
>>> I had kept separate files to affirm the modularity and ease of
>>> portability of the system.
>>>
>>> There are three different interfaces,
>>> 1. The Linux driver interface
>>> 2. The PRU control interface
>>> 3. The McASP serializer interface.
>>>
>>> To maintain modularity, I  had classified the files respectively as :
>>> 1.  pruss_suart.c
>>> 2.  pruss_suart_api.c
>>> 3.  pruss_suart_utils.c
>>>
>>> This is not a single device which can be expressed as a single file,
>>> but functionally different devices logically cascaded together to
>>> work in unison.
>>>
>>> We use the PRU for packet processing, but the actual data is
>>> transmitted/received through the
>>> McASP, which we use as a serializer.
>>>
>>> I feel to combine these disparate functionalities into a single file
>>> will not
>>>
>>> 1. Help better understanding the device. I mean, why should a TTY
>>> UART driver be aware of the McASP or the PRU.
>>> 2. In case of a bug in the API layer or McASP, the driver need not
>>> be touched, thus improve maintainability.
>>> 3. If we need to port it to another Linux version, just editing the
>>> driver file should suffice, this will reduce bugs while porting.
>>
>> If your code is in the kernel tree, you do not need to ever port it to a
>> new version, as it will happen automatically as new kernels are
>> released, so this really isn't anything to worry about.
>>
>>> To me, combining all of these into a single file only creates a
>>> mess. This is the reason I had separated them into different files!!
>>> I don't understand why should it be better to have all of these into
>>> a single file.
>>
>> As Alan stated, just use 3 files in the directory with the other
>> drivers, you don't need a subdir for something small like this.
>>
>> thanks,
>>
>> greg k-h
> 
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