Re: [PATCH v4 14/21] mtdchar: replace deprecated mmap hook with mmap_prepare, clean up

["Vlastimil Babka (SUSE)" <vbabka@kernel.org>]

On 3/20/26 23:39, Lorenzo Stoakes (Oracle) wrote:
> Replace the deprecated mmap callback with mmap_prepare.
> 
> Commit f5cf8f07423b ("mtd: Disable mtdchar mmap on MMU systems") commented
> out the CONFIG_MMU part of this function back in 2012, so after ~14 years
> it's probably reasonable to remove this altogether rather than updating
> dead code.
> 
> Acked-by: Richard Weinberger <richard@nod.at>
> Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>

Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

> ---
>  drivers/mtd/mtdchar.c | 21 +++------------------
>  1 file changed, 3 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
> index 55a43682c567..bf01e6ac7293 100644
> --- a/drivers/mtd/mtdchar.c
> +++ b/drivers/mtd/mtdchar.c
> @@ -1376,27 +1376,12 @@ static unsigned mtdchar_mmap_capabilities(struct file *file)
>  /*
>   * set up a mapping for shared memory segments
>   */
> -static int mtdchar_mmap(struct file *file, struct vm_area_struct *vma)
> +static int mtdchar_mmap_prepare(struct vm_area_desc *desc)
>  {
>  #ifdef CONFIG_MMU
> -	struct mtd_file_info *mfi = file->private_data;
> -	struct mtd_info *mtd = mfi->mtd;
> -	struct map_info *map = mtd->priv;
> -
> -        /* This is broken because it assumes the MTD device is map-based
> -	   and that mtd->priv is a valid struct map_info.  It should be
> -	   replaced with something that uses the mtd_get_unmapped_area()
> -	   operation properly. */
> -	if (0 /*mtd->type == MTD_RAM || mtd->type == MTD_ROM*/) {
> -#ifdef pgprot_noncached
> -		if (file->f_flags & O_DSYNC || map->phys >= __pa(high_memory))
> -			vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> -#endif
> -		return vm_iomap_memory(vma, map->phys, map->size);
> -	}
>  	return -ENODEV;
>  #else
> -	return vma->vm_flags & VM_SHARED ? 0 : -EACCES;
> +	return vma_desc_test(desc, VMA_SHARED_BIT) ? 0 : -EACCES;
>  #endif
>  }
>  
> @@ -1411,7 +1396,7 @@ static const struct file_operations mtd_fops = {
>  #endif
>  	.open		= mtdchar_open,
>  	.release	= mtdchar_close,
> -	.mmap		= mtdchar_mmap,
> +	.mmap_prepare	= mtdchar_mmap_prepare,
>  #ifndef CONFIG_MMU
>  	.get_unmapped_area = mtdchar_get_unmapped_area,
>  	.mmap_capabilities = mtdchar_mmap_capabilities,