I'm sorry for the delay. I got the flu and have difficulties thinking
straight for longer than a few minutes.
Ekaterina Tumanova <tuman...@linux.vnet.ibm.com> writes:
> Add driver functions for geometry and blocksize detection
>
> Signed-off-by: Ekaterina Tumanova <tuman...@linux.vnet.ibm.com>
> ---
> block.c | 26 ++++++++++++++++++++++++++
> include/block/block.h | 20 ++++++++++++++++++++
> include/block/block_int.h | 3 +++
> 3 files changed, 49 insertions(+)
>
> diff --git a/block.c b/block.c
> index a612594..5df35cf 100644
> --- a/block.c
> +++ b/block.c
> @@ -548,6 +548,32 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error
> **errp)
> }
> }
>
> +struct ProbeBlockSize bdrv_probe_blocksizes(BlockDriverState *bs)
> +{
> + BlockDriver *drv = bs->drv;
> + struct ProbeBlockSize err_geo = { .rc = -1 };
> +
> + assert(drv != NULL);
> + if (drv->bdrv_probe_blocksizes) {
> + return drv->bdrv_probe_blocksizes(bs);
> + }
> +
> + return err_geo;
> +}
I'm not sure about "probe". Naming is hard. "get"?
Squashing status and actual payload into a single struct to use as
return type isn't wrong, but unusual. When the payload can't represent
failure conveniently, we usually return status, and write the payload to
a buffer provided by the caller, like this:
int bdrv_get_blocksizes(BlockDriverState *bs,
uint16_t *physical_blk_sz,
uint16_t *logical_blk_sz)
Or, with a struct to hold both sizes:
int bdrv_get_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
Such a struct should ideally be used in other places where we store both
sizes.
A brief function contract comment wouldn't hurt. Something like
/*
* Try to get @bs's logical and physical block size.
* Block sizes are always a multiple of BDRV_SECTOR_SIZE.
* On success, store them in ... and return 0.
* On failure, return -errno.
*/
> +
> +struct ProbeGeometry bdrv_probe_geometry(BlockDriverState *bs)
> +{
> + BlockDriver *drv = bs->drv;
> + struct ProbeGeometry err_geo = { .rc = -1 };
> +
> + assert(drv != NULL);
> + if (drv->bdrv_probe_geometry) {
> + return drv->bdrv_probe_geometry(bs);
> + }
> +
> + return err_geo;
> +}
> +
> /*
> * Create a uniquely-named empty temporary file.
> * Return 0 upon success, otherwise a negative errno value.
> diff --git a/include/block/block.h b/include/block/block.h
> index 5450610..3287dbc 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -60,6 +60,24 @@ typedef enum {
> BDRV_REQ_MAY_UNMAP = 0x4,
> } BdrvRequestFlags;
>
> +struct ProbeBlockSize {
> + int rc;
> + struct BlockSize {
> + uint16_t phys;
> + uint16_t log;
> + } size;
> +};
Use of uint16_t for block sizes is silly, but not your fault, you just
follow existing usage.
> +
> +struct ProbeGeometry {
> + int rc;
> + struct HDGeometry {
> + uint32_t heads;
> + uint32_t sectors;
> + uint32_t cylinders;
> + uint32_t start;
> + } geo;
> +};
> +
> #define BDRV_O_RDWR 0x0002
> #define BDRV_O_SNAPSHOT 0x0008 /* open the file read only and save writes
> in a snapshot */
> #define BDRV_O_TEMPORARY 0x0010 /* delete the file after use */
> @@ -538,6 +556,8 @@ AioContext *bdrv_get_aio_context(BlockDriverState *bs);
> * the old #AioContext is not executing.
> */
> void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context);
> +struct ProbeBlockSize bdrv_probe_blocksizes(BlockDriverState *bs);
> +struct ProbeGeometry bdrv_probe_geometry(BlockDriverState *bs);
>
> void bdrv_io_plug(BlockDriverState *bs);
> void bdrv_io_unplug(BlockDriverState *bs);
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index a1c17b9..830e564 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -271,6 +271,9 @@ struct BlockDriver {
> void (*bdrv_io_unplug)(BlockDriverState *bs);
> void (*bdrv_flush_io_queue)(BlockDriverState *bs);
>
> + struct ProbeBlockSize (*bdrv_probe_blocksizes)(BlockDriverState *bs);
> + struct ProbeGeometry (*bdrv_probe_geometry)(BlockDriverState *bs);
> +
> QLIST_ENTRY(BlockDriver) list;
> };
Callbacks need contracts even more than functions do. I know this file
is full of bad examples. Let's not add more :)
