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Date: Sat, 3 Feb 2024 13:35:28 +0100
From: Stanislaw Gruszka <stf_xl@wp.pl>
To: Kalle Valo <kvalo@kernel.org>
Cc: linux-wireless@vger.kernel.org
Subject: Re: [PATCH 4/4] wifi: rt2x00: fix __le32 sparse warnings
Message-ID: <20240203123528.GA170353@wp.pl>
References: <20240130151556.2315951-1-kvalo@kernel.org>
 <20240130151556.2315951-5-kvalo@kernel.org>
 <87il3aaqoz.fsf@kernel.org>
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In-Reply-To: <87il3aaqoz.fsf@kernel.org>

Hi Kalle

On Wed, Jan 31, 2024 at 09:48:44AM +0200, Kalle Valo wrote:
> Kalle Valo <kvalo@kernel.org> writes:
> 
> > Sparse warns:
> >
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10949:39: warning: incorrect type in assignment (different base types)
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10949:39:    expected unsigned int [usertype]
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10949:39:    got restricted __le32 [usertype]
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10951:43: warning: incorrect type in assignment (different base types)
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10951:43:    expected unsigned int [usertype]
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10951:43:    got restricted __le32 [usertype]
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10953:43: warning: incorrect type in assignment (different base types)
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10953:43:    expected unsigned int [usertype]
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10953:43:    got restricted __le32 [usertype]
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10955:43: warning: incorrect type in assignment (different base types)
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10955:43:    expected unsigned int [usertype]
> > drivers/net/wireless/ralink/rt2x00/rt2800lib.c:10955:43:    got restricted __le32 [usertype]
> >
> > rt2x00 does some wicked casting here so no wonder sparse warns. Clean that up
> > and use cpu_to_le16() to avoid any warnings.
> >
> > Compile tested only.
> >
> > Signed-off-by: Kalle Valo <kvalo@kernel.org>
> 
> Stanislaw, sorry somehow I corrupted your address but fixed it now. Let
> me know what you think, patch here:
> 
> https://patchwork.kernel.org/project/linux-wireless/patch/20240130151556.2315951-5-kvalo@kernel.org/

If I analyse it correctly, patch is not ok on Big Endian machines
where we do bytes swapping.

Let asume reg value is 0x0D0C0B0A

On previous code:

-	*(u32 *)&rt2x00dev->eeprom[i] = cpu_to_le32(reg);

result is

eeprom[0] = 0x0D
eeprom[1] = 0x0C
eeprom[2] = 0x0B
eeprom[3] = 0x0A

After modification:

+	rt2x00dev->eeprom[i] = cpu_to_le16(reg);
+	rt2x00dev->eeprom[i + 1] = cpu_to_le16(upper_16_bits(reg));

result will be

eeprom[0] = 0x0B
eeprom[1] = 0x0A
eeprom[2] = 0x0D
eeprom[2] = 0x0C

Maybe just casting to __le32, i.e:
	
	*(__le32 *)&rt2x00dev->eeprom[i] = cpu_to_le32(reg);

would solve the problem ?

Regards
Stanislaw