[SeaBIOS] [PATCH v5 4/5] QEMU fw_cfg: Add functions for accessing files by key

[Laszlo Ersek]

On 02/18/17 07:21, ben at skyportsystems.com wrote:
> From: Ben Warren <ben at skyportsystems.com>
> 
> When resuming from S3, only fw_cfg file keys are known.
> 
> Signed-off-by: Ben Warren <ben at skyportsystems.com>
> ---
>  src/fw/paravirt.c | 23 +++++++++++++++++++++++
>  src/fw/paravirt.h |  2 ++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
> index 4618647..e513dd5 100644
> --- a/src/fw/paravirt.c
> +++ b/src/fw/paravirt.c
> @@ -352,6 +352,17 @@ qemu_cfg_write_file(void *src, struct romfile_s *file, u32 offset, u32 len)
>      return len;
>  }
>  
> +// Bare-bones function for writing a file knowing only its unique
> +// identifying key (select)
> +int
> +qemu_cfg_write_file_simple(void *src, u16 key, u32 offset, u32 len)
> +{
> +    qemu_cfg_select(key);
> +    qemu_cfg_skip(offset);
> +    qemu_cfg_write(src, len);
> +    return len;
> +}

Does anything counter-indicate the customization seen in
qemu_cfg_write_file() as well, that is, call qemu_cfg_write_entry() if
offset is zero?

If not, then I think you could even split out that part of
qemu_cfg_write_file() as qemu_cfg_write_file_simple(), and call it from
qemu_cfg_write_file().

> +
>  static void
>  qemu_romfile_add(char *name, int select, int skip, int size)
>  {
> @@ -370,6 +381,18 @@ qemu_romfile_add(char *name, int select, int skip, int size)
>  }
>  
>  u16
> +qemu_get_romfile_key(struct romfile_s *file)
> +{
> +    struct qemu_romfile_s *qfile;
> +    qfile = container_of(file, struct qemu_romfile_s, file);

If the input pointer "file" was valid, then container_of() cannot
produce a NULL pointer. So I suggest to drop the code that depends on that.

> +    if (!qfile) {
> +        warn_internalerror();
> +        return 0;
> +    }
> +    return qfile->select;
> +}

This could be reused in qemu_cfg_write_file() too, so that that function
would remain:
- initial checks
- qemu_cfg_write_file_simple( ..., qemu_get_romfile_key(), ...)

I think patch #1 is fine as is, so I'd keep this refactoring in patch #4.

Thanks
Laszlo

> +
> +u16
>  qemu_get_present_cpus_count(void)
>  {
>      u16 smp_count = 0;
> diff --git a/src/fw/paravirt.h b/src/fw/paravirt.h
> index fb220d8..16f3d9a 100644
> --- a/src/fw/paravirt.h
> +++ b/src/fw/paravirt.h
> @@ -56,5 +56,7 @@ void qemu_cfg_init(void);
>  
>  u16 qemu_get_present_cpus_count(void);
>  int qemu_cfg_write_file(void *src, struct romfile_s *file, u32 offset, u32 len);
> +int qemu_cfg_write_file_simple(void *src, u16 key, u32 offset, u32 len);
> +u16 qemu_get_romfile_key(struct romfile_s *file);
>  
>  #endif
>