Re: [Qemu-devel] [RFC PATCH V1 2/2] arm_boot: conditionalised dtb command line update

[Peter Crosthwaite]

On Fri, Jun 1, 2012 at 11:44 AM, Peter Maydell <address@hidden> wrote:
> On 1 June 2012 02:16, Peter A. G. Crosthwaite
> <address@hidden> wrote:
>> @@ -240,10 +241,13 @@ static int load_dtb(target_phys_addr_t addr, const 
>> struct arm_boot_info *binfo)
>>         fprintf(stderr, "couldn't set /memory/reg\n");
>>     }
>>
>> -    rc = qemu_devtree_setprop_string(fdt, "/chosen", "bootargs",
>> -                                      binfo->kernel_cmdline);
>> -    if (rc < 0) {
>> -        fprintf(stderr, "couldn't set /chosen/bootargs\n");
>> +    machine_opts = qemu_opts_find(qemu_find_opts("machine"), 0);
>> +    if (machine_opts && qemu_opt_get(machine_opts, "append")) {
>> +        rc = qemu_devtree_setprop_string(fdt, "/chosen", "bootargs",
>> +                                          binfo->kernel_cmdline);
>> +        if (rc < 0) {
>> +            fprintf(stderr, "couldn't set /chosen/bootargs\n");
>> +        }
>>     }
>
> Can you just check for binfo->kernel_cmdline being NULL or not
> rather than rereading the option via qemu_opt_get? The latter
> seems pretty ugly.
>

No, it wont work,

vl.c will populate it with "\"\"":

    if (machine_opts) {
...
        kernel_cmdline = qemu_opt_get(machine_opts, "append");
    } else {
        kernel_filename = initrd_filename = kernel_cmdline = NULL;
    }

    if (!kernel_cmdline) {
        kernel_cmdline = "";
    }


binfo->kernel_cmdline will not be null on the omission of -append.

I did it this way as its the only way I can see where you can
determine whether or not -apend happened. You could strcmp with "\"\""
and use that as your condition, but then you have a possibly piece of
policy that an empty command means no update (i.e. you should still be
able to explictly -apend "\"\"" to wipe out the dtb command line).

Regards,

Peter

> -- PMM