linux-kernel - Re: [RFC] mtd: Fix error code loss in mtdchar

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Message-ID: <1131184426.81026.1695650583370.JavaMail.zimbra@nod.at>
Date:   Mon, 25 Sep 2023 16:03:03 +0200 (CEST)
From:   Richard Weinberger <richard@....at>
To:     ZhaoLong Wang <wangzhaolong1@...wei.com>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        chengzhihao1 <chengzhihao1@...wei.com>,
        yi zhang <yi.zhang@...wei.com>,
        yangerkun <yangerkun@...wei.com>
Subject: Re: [RFC] mtd: Fix error code loss in mtdchar_read() function.

----- Ursprüngliche Mail -----
> Von: "ZhaoLong Wang" <wangzhaolong1@...wei.com>
> An: "Miquel Raynal" <miquel.raynal@...tlin.com>, "richard" <richard@....at>, "Vignesh Raghavendra" <vigneshr@...com>
> CC: "linux-mtd" <linux-mtd@...ts.infradead.org>, "linux-kernel" <linux-kernel@...r.kernel.org>, "chengzhihao1"
> <chengzhihao1@...wei.com>, "ZhaoLong Wang" <wangzhaolong1@...wei.com>, "yi zhang" <yi.zhang@...wei.com>, "yangerkun"
> <yangerkun@...wei.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;
                }

Thanks,
//richard