cxl: Implement an ioctl to fetch afu card-id, offset-id and mode

Given a file descriptor on an afu device, libcxl currently uses the
major/minor number obtained from fstat on the fd to construct path to
the afu's sysfs directory. However it is possible that rather than using
one of the device in /dev/cxl, a kernel driver creates its own device
which export generic cxl interface to the userspace. This causes
problems with libcxl as it tries to use a wrong major/minor number to
construct the sysfs path and fail.

So this patch introduces a new ioctl called CXL_IOCTL_GET_AFU_ID on the
afu file descriptor to fetch the cxl_afu_id struct that holds the
card/offset-id and mode information. These info is then used by libcxl to
construct the correct path to the afu sysfs directory.

Testing:
	- Build against pseries be/le configs
	- Testing with corresponding libcxl changes to verify that it constructs
	  right sysfs path to the afu.

Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Acked-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 22 insertions, 0 deletions

diff --git a/include/uapi/misc/cxl.h b/include/uapi/misc/cxl.h
index cd6d789b73ec..99a8ca15fe64 100644
--- a/include/uapi/misc/cxl.h
+++ b/include/uapi/misc/cxl.h
@@ -32,10 +32,32 @@ struct cxl_ioctl_start_work {
 #define CXL_START_WORK_ALL              (CXL_START_WORK_AMR |\
                                          CXL_START_WORK_NUM_IRQS)
 
+
+/* Possible modes that an afu can be in */
+#define CXL_MODE_DEDICATED   0x1
+#define CXL_MODE_DIRECTED    0x2
+
+/* possible flags for the cxl_afu_id flags field */
+#define CXL_AFUID_FLAG_SLAVE    0x1  /* In directed-mode afu is in slave mode */
+
+struct cxl_afu_id {
+        __u64 flags;     /* One of CXL_AFUID_FLAG_X */
+        __u32 card_id;
+        __u32 afu_offset;
+        __u32 afu_mode;  /* one of the CXL_MODE_X */
+        __u32 reserved1;
+        __u64 reserved2;
+        __u64 reserved3;
+        __u64 reserved4;
+        __u64 reserved5;
+        __u64 reserved6;
+};
+
 /* ioctl numbers */
 #define CXL_MAGIC 0xCA
 #define CXL_IOCTL_START_WORK            _IOW(CXL_MAGIC, 0x00, struct cxl_ioctl_start_work)
 #define CXL_IOCTL_GET_PROCESS_ELEMENT   _IOR(CXL_MAGIC, 0x01, __u32)
+#define CXL_IOCTL_GET_AFU_ID            _IOR(CXL_MAGIC, 0x02, struct cxl_afu_id)
 
 #define CXL_READ_MIN_SIZE 0x1000 /* 4K */