Messages in this thread | | | Date | Tue, 5 Sep 2006 20:00:06 -0500 | From | "Josh Boyer" <> | Subject | Re: [PATCH] Make MTD chardev mmap available under some circumstances |
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On 9/5/06, David Howells <dhowells@redhat.com> wrote: > > Make it possible to mmap MTD chardevs directly or by copy on a NOMMU system.
Why would you want to do this? I'm just curious.
> +/* > + * Allow NOMMU mmap() to directly map the device (if not NULL) > + * - return the address to which the offset maps > + * - return -ENOSYS to indicate refusal to do the mapping
Where do you actually do the -ENOSYS part? I think that comment belongs to the actual mtd_get_unmapped_area call in mtdchar.c, no?
> +/* > + * try to determine where a shared mapping can be made > + * - only supported for NOMMU at the moment (MMU can't doesn't copy private > + * mappings) > + */ > +#ifndef CONFIG_MMU > +static unsigned long mtd_get_unmapped_area(struct file *file, > + unsigned long addr, > + unsigned long len, > + unsigned long pgoff, > + unsigned long flags) > +{ > + struct mtd_file_info *mfi = file->private_data; > + struct mtd_info *mtd = mfi->mtd; > + > + if (mtd->get_unmapped_area) { > + unsigned long offset; > + > + if (addr != 0) > + return (unsigned long) -EINVAL; > + > + if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT)) > + return (unsigned long) -EINVAL; > + > + offset = pgoff << PAGE_SHIFT; > + if (offset > mtd->size - len) > + return (unsigned long) -EINVAL; > + > + return mtd->get_unmapped_area(mtd, len, offset, flags); > + } > + > + /* can't map directly */ > + return (unsigned long) -ENOSYS; > +} > +#endif
Could we do something like:
#else #define mtd_get_unmapped_area (NULL);
which would prevent the ugly ifdef in the mtd_fops structure?
> static struct file_operations mtd_fops = { > .owner = THIS_MODULE, > .llseek = mtd_lseek, > @@ -771,6 +864,10 @@ static struct file_operations mtd_fops = > .ioctl = mtd_ioctl, > .open = mtd_open, > .release = mtd_close, > + .mmap = mtd_mmap, > +#ifndef CONFIG_MMU > + .get_unmapped_area = mtd_get_unmapped_area, > +#endif
See above.
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