linux-kernel - Re: [PATCH v4 4/5] mtd_blkdevs: add option to enable scanning for partitions

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Message-ID: <871124728.219224.1668111155161.JavaMail.zimbra@nod.at>
Date:   Thu, 10 Nov 2022 21:12:35 +0100 (CET)
From:   Richard Weinberger <richard@....at>
To:     Daniel Golle <daniel@...rotopia.org>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Matthew Wilcox <willy@...radead.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Ming Lei <ming.lei@...hat.com>,
        linux-block <linux-block@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH v4 4/5] mtd_blkdevs: add option to enable scanning for
 partitions

----- Ursprüngliche Mail -----
> On Thu, Nov 10, 2022 at 08:44:53PM +0100, Richard Weinberger wrote:
>> ----- Ursprüngliche Mail -----
>> > Von: "Daniel Golle" <daniel@...rotopia.org>
>> > +
>> > +		if (!IS_ENABLED(CONFIG_MTD_BLOCK_PARTITIONS) || mtd_type_is_nand(new->mtd))
>> > +			gd->flags |= GENHD_FL_NO_PART;
>> 
>> I know that NAND should not get used with mtdblock because lack of wearleveling
>> and
>> in general too many writes. But what exactly is the rationale to deny part
>> scanning for NAND?
> 
> As UBI should be used on NAND, partition scanning should be enabled for
> ubiblock devices to have uImage.FIT filesystem subimages mapped by the
> partition parser.
> 
> If not skipping partition scanning on NAND-backed mtdblock devices the
> scanning itself will already trigger multiple warnings which now happen
> every time when a NAND-backed mtdblock device is being opened since
> commit 96a3295c ("mtdblock: warn if opened on NAND").

I see, you want to promote UBI. Makes sense.
In case you do a v5 series, please add a comment to the code.

Thanks,
//richard