linux-kernel - Re: [PATCH] mtd: Fix mtd not registered due to nvmem name collision

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Message-ID: <20200504104339.31b4a858@xps13>
Date:   Mon, 4 May 2020 10:43:39 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Ricardo Ribalda Delgado <ricardo@...alda.com>
Cc:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Alban Bedel <albeu@...e.fr>,
        Ricardo Ribalda Delgado <ribalda@...nel.org>
Subject: Re: [PATCH] mtd: Fix mtd not registered due to nvmem name collision

Hi Richard,

Ricardo Ribalda Delgado <ricardo@...alda.com> wrote on Thu, 30 Apr 2020
15:17:21 +0200:

> From: Ricardo Ribalda Delgado <ribalda@...nel.org>
> 
> When the nvmem framework is enabled, a nvmem device is created per mtd
> device/partition.
> 
> It is not uncommon that a device can have multiple mtd devices with
> partitions that have the same name. Eg, when there DT overlay is allowed
> and the same device with mtd is attached twice.
> 
> Under that circumstances, the mtd fails to register due to a name
> duplication on the nvmem framework.
> 
> With this patch we use the mtdX name instead of the partition name,
> which is unique.
> 
> [    8.948991] sysfs: cannot create duplicate filename '/bus/nvmem/devices/Production Data'
> [    8.948992] CPU: 7 PID: 246 Comm: systemd-udevd Not tainted 5.5.0-qtec-standard #13
> [    8.948993] Hardware name: AMD Dibbler/Dibbler, BIOS 05.22.04.0019 10/26/2019
> [    8.948994] Call Trace:
> [    8.948996]  dump_stack+0x50/0x70
> [    8.948998]  sysfs_warn_dup.cold+0x17/0x2d
> [    8.949000]  sysfs_do_create_link_sd.isra.0+0xc2/0xd0
> [    8.949002]  bus_add_device+0x74/0x140
> [    8.949004]  device_add+0x34b/0x850
> [    8.949006]  nvmem_register.part.0+0x1bf/0x640
> ...
> [    8.948926] mtd mtd8: Failed to register NVMEM device
> 
> Fixes: c4dfa25ab307 ("mtd: add support for reading MTD devices via the nvmem API")
> Signed-off-by: Ricardo Ribalda Delgado <ribalda@...nel.org>
> ---
>  drivers/mtd/mtdcore.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 2916674208b3..29d41003d6e0 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -555,7 +555,7 @@ static int mtd_nvmem_add(struct mtd_info *mtd)
>  
>  	config.id = -1;
>  	config.dev = &mtd->dev;
> -	config.name = mtd->name;
> +	config.name = dev_name(&mtd->dev);
>  	config.owner = THIS_MODULE;
>  	config.reg_read = mtd_nvmem_reg_read;
>  	config.size = mtd->size;

We hope this will definitely fix the NVMEM duplicate name issue. If it
does not reliably, we might want to revert this patch and create an MTD
unique ID field which, for each MTD device, concatenates the name of
its parent and its own mtd->name.

Acked-by: Miquel Raynal <miquel.raynal@...tlin.com>

Thanks,
Miquèl