Re: [PATCH] drivers/mtd: Fix device registration error

[Boris Brezillon <boris.brezillon@collabora.com>]

Hello Aneesh,

On Tue,  5 Feb 2019 14:35:47 +0530
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote:

> This change helps me to get multiple mtd device registered. Without this
> I get
> 
> sysfs: cannot create duplicate filename '/bus/nvmem/devices/flash0'
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc2-00557-g1ef20ef21f22 #13
> Call Trace:
> [c0000000b38e3220] [c000000000b58fe4] dump_stack+0xe8/0x164 (unreliable)
> [c0000000b38e3270] [c0000000004cf074] sysfs_warn_dup+0x84/0xb0
> [c0000000b38e32f0] [c0000000004cf6c4] sysfs_do_create_link_sd.isra.0+0x114/0x150
> [c0000000b38e3340] [c000000000726a84] bus_add_device+0x94/0x1e0
> [c0000000b38e33c0] [c0000000007218f0] device_add+0x4d0/0x830
> [c0000000b38e3480] [c0000000009d54a8] nvmem_register.part.2+0x1c8/0xb30
> [c0000000b38e3560] [c000000000834530] mtd_nvmem_add+0x90/0x120
> [c0000000b38e3650] [c000000000835bc8] add_mtd_device+0x198/0x4e0
> [c0000000b38e36f0] [c00000000083619c] mtd_device_parse_register+0x11c/0x280
> [c0000000b38e3780] [c000000000840830] powernv_flash_probe+0x180/0x250
> [c0000000b38e3820] [c00000000072c120] platform_drv_probe+0x60/0xf0
> [c0000000b38e38a0] [c0000000007283c8] really_probe+0x138/0x4d0
> [c0000000b38e3930] [c000000000728acc] driver_probe_device+0x13c/0x1b0
> [c0000000b38e39b0] [c000000000728c7c] __driver_attach+0x13c/0x1c0
> [c0000000b38e3a30] [c000000000725130] bus_for_each_dev+0xa0/0x120
> [c0000000b38e3a90] [c000000000727b2c] driver_attach+0x2c/0x40
> [c0000000b38e3ab0] [c0000000007270f8] bus_add_driver+0x228/0x360
> [c0000000b38e3b40] [c00000000072a2e0] driver_register+0x90/0x1a0
> [c0000000b38e3bb0] [c00000000072c020] __platform_driver_register+0x50/0x70
> [c0000000b38e3bd0] [c00000000105c984] powernv_flash_driver_init+0x24/0x38
> [c0000000b38e3bf0] [c000000000010904] do_one_initcall+0x84/0x464
> [c0000000b38e3cd0] [c000000001004548] kernel_init_freeable+0x530/0x634
> [c0000000b38e3db0] [c000000000011154] kernel_init+0x1c/0x168
> [c0000000b38e3e20] [c00000000000bed4] ret_from_kernel_thread+0x5c/0x68
> mtd mtd1: Failed to register NVMEM device
> 
> With the change we now have
> 
> /sys/bus/nvmem/devices# ls -al
> total 0
> drwxr-xr-x 2 root root 0 Feb  5 12:21 .
> drwxr-xr-x 4 root root 0 Feb  5 12:21 ..
> lrwxrwxrwx 1 root root 0 Feb  5 12:21 flash0 -> ../../../devices/platform/ibm,opal:flash@0/mtd/mtd0/flash0
> lrwxrwxrwx 1 root root 0 Feb  5 12:21 flash1 -> ../../../devices/platform/ibm,opal:flash@1/mtd/mtd1/flash1
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>  drivers/mtd/mtdcore.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 999b705769a8..90035da3423c 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -503,10 +503,11 @@ static int mtd_nvmem_reg_read(void *priv, unsigned int offset,
>  	return retlen == bytes ? 0 : -EIO;
>  }
>  
> -static int mtd_nvmem_add(struct mtd_info *mtd)
> +static int mtd_nvmem_add(struct mtd_info *mtd, int i)
>  {
>  	struct nvmem_config config = {};
>  
> +	config.id = i;
>  	config.dev = &mtd->dev;
>  	config.name = mtd->name;

mtd->name should be unique in the first place, otherwise mtdparts
parsing won't work (it's using mtd->name to match the device
partitions should be applied to) and I guess there might be other
issues. I know it's currently not enforced, but this kind of
situation makes me realize we should enforce it.

So the right fix would be to have config.id = -1 and ensure mtd->name
is unique at MTD registration time.

Back to your specific powernv case, using DT node name doesn't work, as
the @<id> suffix is dropped, which means all your flash devices are
named 'flash'.

>  	config.owner = THIS_MODULE;
> @@ -616,7 +617,7 @@ int add_mtd_device(struct mtd_info *mtd)
>  		goto fail_added;
>  
>  	/* Add the nvmem provider */
> -	error = mtd_nvmem_add(mtd);
> +	error = mtd_nvmem_add(mtd, i);
>  	if (error)
>  		goto fail_nvmem_add;
>  

Regards,

Boris

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