ublk_drv: add SET_PARAMS/GET_PARAMS control command

Add two commands to set/get parameters generically.

One important goal of ublk is to provide generic framework for making
block device by userspace flexibly.

As one generic block device, there are still lots of block parameters,
such as max_sectors, write_cache/fua, discard related limits,
zoned parameters, ...., so this patch starts to add generic mechanism
for set/get device parameters.

Both generic block parameters(all kinds of queue settings) and ublk
feature parameters can be covered with this way, then it becomes quite
easy to extend in future.

Add two parameter types are used so far: basic(covers basic queue setting
and misc settings which can't be grouped easily) and discard, basic type
must be set, and discard type becomes optional now

This way provides mechanism to simulate any kind of generic block device
from userspace easily, from both block queue setting viewpoint or ublk
feature viewpoint.

The style of putting all parameters together is suggested by Christoph.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220730092750.1118167-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 47 insertions, 0 deletions

diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index ca33092354ab..54d065426f06 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -15,6 +15,8 @@
 #define	UBLK_CMD_DEL_DEV		0x05
 #define	UBLK_CMD_START_DEV	0x06
 #define	UBLK_CMD_STOP_DEV	0x07
+#define	UBLK_CMD_SET_PARAMS	0x08
+#define	UBLK_CMD_GET_PARAMS	0x09
 
 /*
  * IO commands, issued by ublk server, and handled by ublk driver.
@@ -158,4 +160,49 @@ struct ublksrv_io_cmd {
 	__u64	addr;
 };
 
+struct ublk_param_basic {
+#define UBLK_ATTR_READ_ONLY            (1 << 0)
+#define UBLK_ATTR_ROTATIONAL           (1 << 1)
+#define UBLK_ATTR_VOLATILE_CACHE       (1 << 2)
+#define UBLK_ATTR_FUA                  (1 << 3)
+	__u32	attrs;
+	__u8	logical_bs_shift;
+	__u8	physical_bs_shift;
+	__u8	io_opt_shift;
+	__u8	io_min_shift;
+
+	__u32	max_sectors;
+	__u32	chunk_sectors;
+
+	__u64   dev_sectors;
+	__u64   virt_boundary_mask;
+};
+
+struct ublk_param_discard {
+	__u32	discard_alignment;
+
+	__u32	discard_granularity;
+	__u32	max_discard_sectors;
+
+	__u32	max_write_zeroes_sectors;
+	__u16	max_discard_segments;
+	__u16	reserved0;
+};
+
+struct ublk_params {
+	/*
+	 * Total length of parameters, userspace has to set 'len' for both
+	 * SET_PARAMS and GET_PARAMS command, and driver may update len
+	 * if two sides use different version of 'ublk_params', same with
+	 * 'types' fields.
+	 */
+	__u32	len;
+#define UBLK_PARAM_TYPE_BASIC           (1 << 0)
+#define UBLK_PARAM_TYPE_DISCARD         (1 << 1)
+	__u32	types;			/* types of parameter included */
+
+	struct ublk_param_basic		basic;
+	struct ublk_param_discard	discard;
+};
+
 #endif