Hi Alexander,
On Sunday 03 January 2010 22:31:46 Alexander Clouter wrote:
> In gmane.linux.drivers.mtd David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote:
> > On Sun, 2010-01-03 at 21:17 +0100, Florian Fainelli wrote:
> >> This patch modifies the physmap-flash driver to include
> >> the ar7part partition parser in the list of parsers to
> >> use when a physmap-flash driver is registered. This is
> >> required for AR7 to create partitions correctly.
> >
> > Hrm, perhaps we'd do better to allow the probe types to be specified in
> > the platform physmap_flash_data?
>
> I am not completely convinced the ar7part approach is the best way as
> you are:
> 1) not actually reading a partition table and instead using a bunch of
> 'magic' values to try to work out the partition layout
> 2) it bears no resemble to what is seen by the ADAM2 bootloader
> 3) regardless of whether you would actually want to, the user is unable
> to amend the partition table and have Linux automagically set
> the table apprioately
>
> I chatted with Florian a while back about this but we never continued
> with it (Real Life[tm] seemed to get in the way) but I had cobbled the
> following together:
> ----
> diff --git a/arch/mips/ar7/platform.c b/arch/mips/ar7/platform.c
> index e2278c0..df33fea 100644
> --- a/arch/mips/ar7/platform.c
> +++ b/arch/mips/ar7/platform.c
> @@ -24,6 +24,7 @@
> #include <linux/dma-mapping.h>
> #include <linux/platform_device.h>
> #include <linux/mtd/physmap.h>
> +#include <linux/mtd/partitions.h>
> #include <linux/serial.h>
> #include <linux/serial_8250.h>
> #include <linux/ioport.h>
> @@ -467,6 +468,60 @@ static void cpmac_get_mac(int instance, unsigned char
> *dev_addr) char2hex(mac[i * 3 + 1]);
> }
>
> +static void __init detect_partitions(void)
> +{
> + unsigned int i, start, end;
> + int ret;
> + char mtdenv[5], *buf;
> +
> + for (physmap_flash_data.nr_parts = 0;
> + physmap_flash_data.nr_parts < 10;
> + physmap_flash_data.nr_parts++) {
> + sprintf(mtdenv, "mtd%d", physmap_flash_data.nr_parts);
> + if (!prom_getenv(mtdenv))
> + break;
> + }
> +
> + if (physmap_flash_data.nr_parts == 0) {
> + printk(KERN_INFO "No partitions found for physmap MTD\n");
> + return;
> + }
> + if (physmap_flash_data.nr_parts == 10)
> + printk(KERN_INFO "Reached nr_parts limit for physmap MTD\n");
> +
> + physmap_flash_data.parts = kzalloc(
> + sizeof(struct mtd_partition)*physmap_flash_data.nr_parts,
> + GFP_KERNEL);
> + if (!physmap_flash_data.parts) {
> + printk(KERN_ERR "Unable to alloc physmap MTD parts struct\n");
> + return;
> + }
> +
> + for (i = 0; i < physmap_flash_data.nr_parts; i++) {
> + sprintf(mtdenv, "mtd%d", i);
> + buf = prom_getenv(mtdenv);
> +
> + ret = sscanf(buf, "%x,%x", &start, &end);
> + if (ret != 2 || start < 0x90000000 || start > 0x90400000
> + || end < 0x90000000 || end > 0x90400000
> + || start > end) {
> + printk(KERN_WARNING "broken partition table for physmap\n");
> + kfree(physmap_flash_data.parts);
> + physmap_flash_data.parts = NULL;
> + physmap_flash_data.nr_parts = 0;
> + return;
> + }
> +
> + start -= 0x90000000;
> + end -= 0x90000000;
> +
> + physmap_flash_data.parts[i].name = NULL;
> + physmap_flash_data.parts[i].size = end - start;
> + physmap_flash_data.parts[i].offset = start;
> + physmap_flash_data.parts[i].mask_flags = MTD_WRITEABLE;
> + }
> +}
> +
> static void __init detect_leds(void)
> {
> char *prid, *usb_prod;
> @@ -536,6 +591,7 @@ static int __init ar7_register_devices(void)
> return res;
> }
> #endif /* CONFIG_SERIAL_8250 */
> + detect_partitions();
> res = platform_device_register(&physmap_flash);
> if (res)
> return res;
> ----
>
> It simply pulls apart the 'PROM' (aka ADAM2) config and uses that to
> build the partition table.
This is indeed simple but if I recall right the rationale behind ar7part was
to create a sane partition layout no matter if the bootloader was ADAM2 or
PSPBoot and the root filesystem type. JFFS2 and squashfs do not have the same
erase-block size alignment constraints, ar7part deals with that too.
When we last chatted about that I did not recall exactly those details.
--
Regards, Florian
