linux-kernel - Re: [PATCH] usb: gadget: Add the console support for usb-to-serial port

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Date:	Wed, 18 Nov 2015 20:45:45 +0800
From:	Baolin Wang <baolin.wang@...aro.org>
To:	David Laight <David.Laight@...lab.com>
Cc:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"r.baldyga@...sung.com" <r.baldyga@...sung.com>,
	"fabio.estevam@...escale.com" <fabio.estevam@...escale.com>,
	Philip Oberstaller <Philip.Oberstaller@...tentrio.com>,
	Peter Hurley <peter@...leysoftware.com>,
	"scottwood@...escale.com" <scottwood@...escale.com>,
	Mark Brown <broonie@...nel.org>,
	USB <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: gadget: Add the console support for usb-to-serial port

On 18 November 2015 at 20:05, David Laight <David.Laight@...lab.com> wrote:
> From: Baolin Wang
>> Sent: 18 November 2015 10:45
>> On 18 November 2015 at 17:32, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>> > On Wed, Nov 18, 2015 at 4:15 AM, Baolin Wang <baolin.wang@...aro.org> wrote:
>> >> On 17 November 2015 at 21:34, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>> >>> On Mon, Nov 16, 2015 at 9:05 AM, Baolin Wang <baolin.wang@...aro.org> wrote:
>> >>>> It dose not work when we want to use the usb-to-serial port based
>> >>>> on one usb gadget as a console. Thus this patch adds the console
>> >>>> initialization to support this request.
>> >>>
>> >
>> >>>> +#define GS_BUFFER_SIZE         (4096)
>> >>> Redundant parens
>> >> OK. I'll remove it.
>> >>
>> >>>> +#define GS_CONSOLE_BUF_SIZE    (2 * GS_BUFFER_SIZE)
>> >>>> +
>> >>>> +struct gscons_info {
>> >>>> +       struct gs_port          *port;
>> >>>> +       struct tty_driver       *tty_driver;
>> >>>> +       struct work_struct      work;
>> >>>> +       int                     buf_tail;
>> >>>> +       char                    buf[GS_CONSOLE_BUF_SIZE];
>> >>>
>> >>> Can't be malloced once?
>> >> The 'gscons_info' structure is malloced once.
>> >
>> > In state of high fragmentation is quite hard to find big memory chunks.
>> > I would split it to two allocations, though if maintainers are okay
>> > with your code, then I'm also okay.
>> >
>>
>> Make sense. But I think the major memory of the 'struct gscons_info'
>> is for the 'buf' member, so I still think no need to allocate it 2
>> times.
>
> It may be worth just reducing GS_BUFFER_SIZE slightly so that the gscons_info
> structure itself is less than 8k.
> If you can't get 2 adjacent pages then a lot of things will fail.
>

But its allocation is called in early booting time, I think there are
not many memory fragments now.

>         David
>



-- 
Baolin.wang
Best Regards
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