Re: [PATCH 1/2] mem: multiple resource support allow exclude a resource

From: Sascha Hauer <s.hauer@pengutronix.de>
To: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH 1/2] mem: multiple resource support allow exclude a resource
Date: Fri, 19 Nov 2010 09:24:35 +0100	[thread overview]
Message-ID: <20101119082435.GB6017@pengutronix.de> (raw)
In-Reply-To: <1290002365-22712-1-git-send-email-plagnioj@jcrosoft.com>

On Wed, Nov 17, 2010 at 02:59:24PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> introduce DEVFS_MEM_BAREBOX_ONLY for this purpose
> 
> Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
> ---
>  arch/arm/lib/armlinux.c |    4 ++++
>  include/driver.h        |    1 +
>  2 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/lib/armlinux.c b/arch/arm/lib/armlinux.c
> index b74c5e8..55d1401 100644
> --- a/arch/arm/lib/armlinux.c
> +++ b/arch/arm/lib/armlinux.c
> @@ -79,6 +79,10 @@ static void setup_memory_tags(void)
>  	list_for_each_entry(mem, &memory_list, list) {
>  		for (i = 0; i < mem->dev->num_resources; i++) {
>  			res = &mem->dev->resource[i];
> +
> +			if (res->flags & DEVFS_MEM_BAREBOX_ONLY)
> +				break;

Shouldn't this be a 'continue'?

> +
>  			params->hdr.tag = ATAG_MEM;
>  			params->hdr.size = tag_size(tag_mem32);
>  
> diff --git a/include/driver.h b/include/driver.h
> index c7dce1e..e98455c 100644
> --- a/include/driver.h
> +++ b/include/driver.h
> @@ -354,6 +354,7 @@ ssize_t cdev_write(struct cdev *cdev, const void *buf, size_t count, ulong offse
>  #define DEVFS_PARTITION_READONLY	(1 << 1)
>  #define DEVFS_IS_PARTITION		(1 << 2)
>  #define DEVFS_RDWR			(1 << 3)
> +#define DEVFS_MEM_BAREBOX_ONLY		(1 << 4)

I realize this when looking at this patch: You should abuse the flags
field in a resource pass custom bits. The only flags in a resource should
be the ones defined in include/linux/ioport.h.
With DEVFS_RDWR you are lucky, there is a IORESOURCE_MEM_WRITEABLE flag
which can be used for this purpose. There is no correspondent flag for
DEVFS_MEM_BAREBOX_ONLY though.

Overall I'm not very happy with the multiple-resources-to-mem-driver
approach. If you are concerned with the overhead of multiple statically
allocated devices we could introduce a add_memory_device(char *name, void *start,
size_t size, unsigned long flags) function which dynamically allocates a
device.

I'm also not convinced that these few multiple statically allocated
devices introduce an overhead at all, I mean most boards only have
SDRAM (one device) and maybe an SRAM (second device).

Sascha

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