linux-kernel - Re: [PATCH 4/5] staging: ft1000: Fix coding style in write_blk

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Date:	Wed, 26 Jan 2011 14:34:59 +0100
From:	Belisko Marek <marek.belisko@...il.com>
To:	Dan Carpenter <error27@...il.com>,
	Marek Belisko <marek.belisko@...n-nandra.com>, gregkh@...e.de,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] staging: ft1000: Fix coding style in write_blk_fifo() function.

On Wed, Jan 26, 2011 at 2:07 PM, Dan Carpenter <error27@...il.com> wrote:
> You didn't introduce it but do you know what the code is trying to do
> here?
>
>        byte_length = word_length * 4;
>
>        if (byte_length % 4)
>                aligncnt = 4 - (byte_length % 4);
>        else
>                aligncnt = 0;
>        byte_length += aligncnt;
>
>        if (byte_length && ((byte_length % 64) == 0))
>                byte_length += 4;
>
>        if (byte_length < 64)
>                byte_length = 68;
>
>
> Apparently the stuff has to be aligned to 4 bytes, but it can't be
> aligned at 64 bytes and it can't be less than 68 bytes long.  The
> part that especially confuses me is why it can't be aligned at 64 bytes.
Yes this code seems little bit confusing but basically this routine send data
to device when firmware code is downloaded. Length which should be send is
asked by device itself (word_length) so maybe it should be somehow
aligned in some cases
(don't know details).  Just to get some idea about length I add some
printk(before 4*word_length
and after byte_length is counted before sending to usb):

Jan 26 14:22:24 linux kernel: [29632.843980] write_blk_fifo: word_length:4
Jan 26 14:22:24 linux kernel: [29632.843984] write_blk_fifo: byte_length:68
Jan 26 14:22:24 linux kernel: [29632.859982] write_blk_fifo: word_length:506
Jan 26 14:22:24 linux kernel: [29632.859986] write_blk_fifo: byte_length:2024
Jan 26 14:22:24 linux kernel: [29632.874984] write_blk_fifo: word_length:505
Jan 26 14:22:24 linux kernel: [29632.874988] write_blk_fifo: byte_length:2020
Jan 26 14:22:24 linux kernel: [29632.890046] write_blk_fifo: word_length:4
Jan 26 14:22:24 linux kernel: [29632.890051] write_blk_fifo: byte_length:68


>
> regards,
> dan carpenter
>

thanks,

marek

-- 
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