Re: [PATCH linux-next (v3) 1/3] MIPS: bcm963xx: Add Broadcom BCM963xx board nvram data structure

On 11/12/15 22:02, Jonas Gorski wrote:

Hi,

On Fri, Dec 11, 2015 at 10:54 PM, Simon Arlott [off-list ref] wrote:

quoted

Broadcom BCM963xx boards have multiple nvram variants across different
SoCs with additional checksum fields added whenever the size of the
nvram was extended.

Add this structure as a header file so that multiple drivers and userspace
can use it.

Signed-off-by: Simon Arlott <redacted>
---
v3: Fix includes/type names, add comments explaining the nvram struct.

v2: Use external struct bcm963xx_nvram definition for bcm963268part.

 MAINTAINERS                         |  1 +
 include/uapi/linux/bcm963xx_nvram.h | 53 +++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 include/uapi/linux/bcm963xx_nvram.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 6b6d4e2e..abf18b4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -2393,6 +2393,7 @@ F:        drivers/irqchip/irq-bcm63*
 F:     drivers/irqchip/irq-bcm7*
 F:     drivers/irqchip/irq-brcmstb*
 F:     include/linux/bcm63xx_wdt.h
+F:     include/uapi/linux/bcm963xx_nvram.h

 BROADCOM TG3 GIGABIT ETHERNET DRIVER
 M:     Prashant Sreedharan <prashant-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>

diff --git a/include/uapi/linux/bcm963xx_nvram.h b/include/uapi/linux/bcm963xx_nvram.h
new file mode 100644
index 0000000..2dcb307
--- /dev/null
+++ b/include/uapi/linux/bcm963xx_nvram.h

Why uapi? The nvram layout isn't really enforced to be that way, and
at least Huawei uses a modified one on some devices (in case you
wondered why bcm63xx doesn't fail a crc32-"broken" one), so IMHO it
should be kept for in-kernel use only.

Because Florian suggested include/uapi/linux/bcm963xx_nvram.h; I could
move it to include/linux/ instead if this is preferred.

quoted

@@ -0,0 +1,53 @@
+#ifndef _UAPI__LINUX_BCM963XX_NVRAM_H__
+#define _UAPI__LINUX_BCM963XX_NVRAM_H__
+
+#include <linux/types.h>
+#include <linux/if_ether.h>
+
+/*
+ * Broadcom BCM963xx SoC board nvram data structure.
+ *
+ * The nvram structure varies in size depending on the SoC board version. Use
+ * the appropriate minimum BCM963XX_NVRAM_*_SIZE define for the information
+ * you need instead of sizeof(struct bcm963xx_nvram) as this may change.
+ *
+ * The "version" field value maps directly to the size and checksum names, e.g.
+ * version 4 uses "checksum_v4" and the data is BCM963XX_NVRAM_V4_SIZE bytes.
+ *
+ * Do not use the __reserved fields, especially not as an offset for CRC
+ * calculations (use BCM963XX_NVRAM_*_SIZE instead). These may be removed or
+ * repositioned.
+ */
+
+#define BCM963XX_NVRAM_V4_SIZE         300
+#define BCM963XX_NVRAM_V5_SIZE         1024
+#define BCM963XX_NVRAM_V6_SIZE         BCM963XX_NVRAM_V5_SIZE
+#define BCM963XX_NVRAM_V7_SIZE         3072
+
+#define BCM963XX_NVRAM_NR_PARTS                5
+
+struct bcm963xx_nvram {
+       __u32   version;
+       char    bootline[256];
+       char    name[16];
+       __u32   main_tp_number;
+       __u32   psi_size;
+       __u32   mac_addr_count;
+       __u8    mac_addr_base[ETH_ALEN];
+       __u8    __reserved1[2];
+       __u32   checksum_v4;
+
+       __u8    __reserved2[292];
+       __u32   nand_part_offset[BCM963XX_NVRAM_NR_PARTS];
+       __u32   nand_part_size[BCM963XX_NVRAM_NR_PARTS];
+       __u8    __reserved3[388];
+       union {
+               __u32   checksum_v5;
+               __u32   checksum_v6;
+       };

what's the point of this union? Both are the same size and have the
same function.

For convenience when deciding which size of nvram to use.

The mach-bcm63xx code uses the V5 definitions because it supports
checksums at the v4 and v5 sizes.

The bcm963xxpart code uses the V6 definitions because that's what my
board has and I can't tell if the nand_part values are valid in version
5 or if they were only added in version 6.
 

quoted

+
+       __u8    __reserved4[2044];
+       __u32   checksum_v7;
+} __packed;

Why is it __packed? there are no unaligned members, so it should work
fine without this (and it did for bcm63xx).

I could remove it, but as soon as someone adds an unaligned member but
forgets to add __packed it's going to break.

There are unaligned members in some of the __reserved areas, like this
one:

#define NVRAM_GPON_SERIAL_NUMBER_LEN    13
#define NVRAM_GPON_PASSWORD_LEN         11

    char gponSerialNumber[NVRAM_GPON_SERIAL_NUMBER_LEN];
    char gponPassword[NVRAM_GPON_PASSWORD_LEN];

-- 
Simon Arlott