cxl/mem: Enable commands via CEL

CXL devices identified by the memory-device class code must implement
the Device Command Interface (described in 8.2.9 of the CXL 2.0 spec).
While the driver already maintains a list of commands it supports, there
is still a need to be able to distinguish between commands that the
driver knows about from commands that are optionally supported by the
hardware.

The Command Effects Log (CEL) is specified in the CXL 2.0 specification.
The CEL is one of two types of logs, the other being vendor specific.
They are distinguished in hardware/spec via UUID. The CEL is useful for
2 things:
1. Determine which optional commands are supported by the CXL device.
2. Enumerate any vendor specific commands

The CEL is used by the driver to determine which commands are available
in the hardware and therefore which commands userspace is allowed to
execute. The set of enabled commands might be a subset of commands which
are advertised in UAPI via CXL_MEM_SEND_COMMAND IOCTL.

With the CEL enabling comes a internal flag to indicate a base set of
commands that are enabled regardless of CEL. Such commands are required
for basic interaction with the hardware and thus can be useful in debug
cases, for example if the CEL is corrupted.

The implementation leaves the statically defined table of commands and
supplements it with a bitmap to determine commands that are enabled.
This organization was chosen for the following reasons:
- Smaller memory footprint. Doesn't need a table per device.
- Reduce memory allocation complexity.
- Fixed command IDs to opcode mapping for all devices makes development
  and debugging easier.
- Certain helpers are easily achievable, like cxl_for_each_cmd().

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com> (v2)
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> (v3)
Link: https://lore.kernel.org/r/20210217040958.1354670-7-ben.widawsky@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 8fd4a177fe25..6f14838c2d25 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -69,6 +69,7 @@ struct cxl_memdev;
  *                (CXL 2.0 8.2.8.4.3 Mailbox Capabilities Register)
  * @mbox_mutex: Mutex to synchronize mailbox access.
  * @firmware_version: Firmware version for the memory device.
+ * @enabled_commands: Hardware commands found enabled in CEL.
  * @pmem_range: Persistent memory capacity information.
  * @ram_range: Volatile memory capacity information.
  */
@@ -84,6 +85,7 @@ struct cxl_mem {
 	size_t payload_size;
 	struct mutex mbox_mutex; /* Protects device mailbox and firmware */
 	char firmware_version[0x10];
+	unsigned long *enabled_cmds;
 
 	struct range pmem_range;
 	struct range ram_range;