linux-kernel - Re: [RFC PATCH] staging: rtl8723au: fix byte order problems

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Date:	Tue, 05 Jan 2016 10:53:36 -0500
From:	Jes Sorensen <Jes.Sorensen@...hat.com>
To:	Julian Calaby <julian.calaby@...il.com>
Cc:	Sven Dziadek <sven.dziadek@....de>,
	Larry Finger <Larry.Finger@...inger.net>,
	Greg KH <gregkh@...uxfoundation.org>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	"devel\@driverdev.osuosl.org" <devel@...verdev.osuosl.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] staging: rtl8723au: fix byte order problems

Julian Calaby <julian.calaby@...il.com> writes:
> Hi Sven,
>
> On Tue, Jan 5, 2016 at 2:29 AM, Sven Dziadek <sven.dziadek@....de> wrote:
>> diff --git a/drivers/staging/rtl8723au/hal/rtl8723a_cmd.c b/drivers/staging/rtl8723au/hal/rtl8723a_cmd.c
>> index 1662c03c..57f5941 100644
>> --- a/drivers/staging/rtl8723au/hal/rtl8723a_cmd.c
>> +++ b/drivers/staging/rtl8723au/hal/rtl8723a_cmd.c
>> @@ -93,11 +93,9 @@ int FillH2CCmd(struct rtw_adapter *padapter, u8 ElementID, u32 CmdLen,
>>
>>                 if (h2c_cmd & BIT(7)) {
>>                         msgbox_ex_addr = REG_HMEBOX_EXT_0 + (h2c_box_num * EX_MESSAGE_BOX_SIZE);
>> -                       h2c_cmd_ex = le16_to_cpu(h2c_cmd_ex);
>>                         rtl8723au_write16(padapter, msgbox_ex_addr, h2c_cmd_ex);
>>                 }
>>                 msgbox_addr = REG_HMEBOX_0 + (h2c_box_num * MESSAGE_BOX_SIZE);
>> -               h2c_cmd = le32_to_cpu(h2c_cmd);
>>                 rtl8723au_write32(padapter, msgbox_addr, h2c_cmd);
>
> While Jes has NACK'd this change, it does highlight that the h2c_cmd
> and h2c_cmd_ex variables are being used to hold both cpu-endian and
> little-endian data. A worthwhile change here might be to move the
> conversion into the function call following these lines so that they
> remain "clean".
>
> That said, I'm not sure this particular snippet of code would work on
> big-endian at all as I'm pretty sure that BIT() produces cpu-endian
> values and we know from the line you remove that h2c_cmd is
> little-endian at this point.

I am not opposed to cleaning it up, however I hope we can just remove
all of the code down the line instead. You may want to look at the h2c
implementation I did for rtl8xxxu. I believe it does work on big-endian,
at least I know Larry has been able to test it on big-endian systems.

Cheers,
Jes
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