[RFC] mtd: Fix error code loss in mtdchar_read() function.

[Miquel Raynal]

Hi Richard,

richard at nod.at wrote on Mon, 25 Sep 2023 16:03:03 +0200 (CEST):

> ----- Ursprüngliche Mail -----
> > Von: "ZhaoLong Wang" <wangzhaolong1 at huawei.com>
> > An: "Miquel Raynal" <miquel.raynal at bootlin.com>, "richard" <richard at nod.at>, "Vignesh Raghavendra" <vigneshr at ti.com>
> > CC: "linux-mtd" <linux-mtd at lists.infradead.org>, "linux-kernel" <linux-kernel at vger.kernel.org>, "chengzhihao1"
> > <chengzhihao1 at huawei.com>, "ZhaoLong Wang" <wangzhaolong1 at huawei.com>, "yi zhang" <yi.zhang at huawei.com>, "yangerkun"
> > <yangerkun at huawei.com>
> > Gesendet: Samstag, 23. September 2023 02:58:56
> > Betreff: [RFC] mtd: Fix error code loss in mtdchar_read() function.  
> 
> > In the first while loop, if the mtd_read() function returns -EBADMSG
> > and 'retlen' returns 0, the loop break and the function returns value
> > 'total_retlen' is 0, not the error code.  
> 
> Given this a second thought. I don't think a NAND driver is allowed to return
> less than requests bytes and setting EBADMSG.
> UBI's IO path has a comment on that:
> 
>                 /*
>                  * The driver should never return -EBADMSG if it failed to read
>                  * all the requested data. But some buggy drivers might do
>                  * this, so we change it to -EIO.
>                  */
>                 if (read != len && mtd_is_eccerr(err)) {
>                         ubi_assert(0);
>                         err = -EIO;
>                 }

Interesting. Shall we add this check to the mtd_read() path as well?

Maybe with a WARN_ON()?

Thanks,
Miquèl