Re: RFC: memmap() now returns NULL on failure.

[Sascha Hauer <s.hauer@pengutronix.de>]

On Sat, May 05, 2012 at 11:45:07PM +0200, Krzysztof Halasa wrote:
> Originally, most callers expected -1 while some thought they'd get NULL
> on failure. NULL seems cleaner to me.

Unix mmap also returns (void *)-1, so returning this value is not that
unusual. I think we should keep this and fix the error checks instead,
for the reason you mention below.

Sascha

> 
> Of course is we want to allow memmapping of "/dev/ram" or something
> alike then we can't apply this patch, we need to fix the NULL-expecters
> instead. Alternatively we could pass &mem as an argument (that's what
> individual fs memmap implementations do).
> 
> Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>
> 
> diff --git a/arch/arm/lib/bootu.c b/arch/arm/lib/bootu.c
> index 0d155cb..478525e 100644
> --- a/arch/arm/lib/bootu.c
> +++ b/arch/arm/lib/bootu.c
> @@ -17,7 +17,7 @@ static int do_bootu(int argc, char *argv[])
>  
>  	fd = open(argv[1], O_RDONLY);
>  	if (fd > 0)
> -		kernel = (void *)memmap(fd, PROT_READ);
> +		kernel = memmap(fd, PROT_READ);
>  
>  	if (!kernel)
>  		kernel = (void *)simple_strtoul(argv[1], NULL, 0);
> diff --git a/commands/bmp.c b/commands/bmp.c
> index 4130474..97e5877 100644
> --- a/commands/bmp.c
> +++ b/commands/bmp.c
> @@ -74,7 +74,7 @@ static int do_bmp(int argc, char *argv[])
>  	}
>  
>  	fb = memmap(fd, PROT_READ | PROT_WRITE);
> -	if (fb == (void *)-1) {
> +	if (fb == NULL) {
>  		perror("memmap");
>  		goto failed_memmap;
>  	}
> diff --git a/commands/go.c b/commands/go.c
> index e9e9d40..11b0cff 100644
> --- a/commands/go.c
> +++ b/commands/go.c
> @@ -49,7 +49,7 @@ static int do_go(int argc, char *argv[])
>  		}
>  
>  		addr = memmap(fd, PROT_READ);
> -		if (addr == (void *)-1) {
> +		if (addr == NULL) {
>  			perror("memmap");
>  			goto out;
>  		}
> diff --git a/common/digest.c b/common/digest.c
> index a327395..7cc5dc3 100644
> --- a/common/digest.c
> +++ b/common/digest.c
> @@ -97,7 +97,7 @@ int digest_file_window(struct digest *d, char *filename,
>  	}
>  
>  	buf = memmap(fd, PROT_READ);
> -	if (buf == (void *)-1) {
> +	if (buf == NULL) {
>  		buf = xmalloc(4096);
>  		flags = 1;
>  	}
> diff --git a/fs/fs.c b/fs/fs.c
> index 04dace4..4ebd2bc 100644
> --- a/fs/fs.c
> +++ b/fs/fs.c
> @@ -781,7 +781,7 @@ void *memmap(int fd, int flags)
>  	struct device_d *dev;
>  	struct fs_driver_d *fsdrv;
>  	FILE *f = &files[fd];
> -	void *ret = (void *)-1;
> +	void *ret = NULL;
>  
>  	if (check_fd(fd))
>  		return ret;
> 
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