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

[Simon Arlott <simon@fire.lp0.eu>]

On 11/12/15 22:02, Jonas Gorski wrote:
> Hi,
> 
> On Fri, Dec 11, 2015 at 10:54 PM, Simon Arlott <simon@fire.lp0.eu> wrote:
>> 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 <simon@fire.lp0.eu>
>> ---
>> 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@broadcom.com>
>> 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.

>> @@ -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.
 
>> +
>> +       __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