Re: [PATCH v2 15/17] cxl: Userspace header file.
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2014-10-02 06:02:40
Also in:
lkml
On Tue, 2014-30-09 at 10:35:04 UTC, Michael Neuling wrote:
quoted hunk ↗ jump to hunk
From: Ian Munsie <redacted> This defines structs and magic numbers required for userspace to interact with the kernel cxl driver via /dev/cxl/afu0.0.diff --git a/include/uapi/misc/cxl.h b/include/uapi/misc/cxl.h new file mode 100644 index 0000000..6a394b5 --- /dev/null +++ b/include/uapi/misc/cxl.h@@ -0,0 +1,88 @@ +/* + * Copyright 2014 IBM Corp. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#ifndef _UAPI_ASM_CXL_H +#define _UAPI_ASM_CXL_H + +#include <linux/types.h> +#include <linux/ioctl.h> + +/* ioctls */ +struct cxl_ioctl_start_work { + __u64 wed; + __u64 amr; + __u64 reserved1; + __u32 reserved2; + __s16 num_interrupts; /* -1 = use value from afu descriptor */ + __u16 process_element; /* returned from kernel */ + __u64 reserved3; + __u64 reserved4; + __u64 reserved5; + __u64 reserved6;
Why so many reserved fields? What mechanism is there that will allow you to ever unreserve them? ie. how does a new userspace detect that the kernel it's running on supports new fields? Or conversely how does a new kernel detect that userspace has passed it a meaningful value in one of the previously reserved fields?
+#define CXL_MAGIC 0xCA +#define CXL_IOCTL_START_WORK _IOWR(CXL_MAGIC, 0x00, struct cxl_ioctl_start_work)
What happened to 0x1 ?
+#define CXL_IOCTL_CHECK_ERROR _IO(CXL_MAGIC, 0x02)
+
+/* events from read() */
+
+enum cxl_event_type {
+ CXL_EVENT_READ_FAIL = -1,I don't see this used?
+ CXL_EVENT_RESERVED = 0,
+ CXL_EVENT_AFU_INTERRUPT = 1,
+ CXL_EVENT_DATA_STORAGE = 2,
+ CXL_EVENT_AFU_ERROR = 3,
+};
+
+struct cxl_event_header {
+ __u32 type;
+ __u16 size;
+ __u16 process_element;
+ __u64 reserved1;
+ __u64 reserved2;
+ __u64 reserved3;
+};Again lots of reserved fields?
+struct cxl_event_afu_interrupt {
+ struct cxl_event_header header;
+ __u16 irq; /* Raised AFU interrupt number */
+ __u16 reserved1;
+ __u32 reserved2;
+ __u64 reserved3;
+ __u64 reserved4;
+ __u64 reserved5;
+};
+
+struct cxl_event_data_storage {
+ struct cxl_event_header header;
+ __u64 addr;
+ __u64 reserved1;
+ __u64 reserved2;
+ __u64 reserved3;
+};
+
+struct cxl_event_afu_error {
+ struct cxl_event_header header;
+ __u64 err;
+ __u64 reserved1;
+ __u64 reserved2;
+ __u64 reserved3;
+};
+
+struct cxl_event {
+ union {
+ struct cxl_event_header header;
+ struct cxl_event_afu_interrupt irq;
+ struct cxl_event_data_storage fault;
+ struct cxl_event_afu_error afu_err;
+ };
+};
Rather than having the header included in every event, would it be clearer if
the cxl_event was:
struct cxl_event {
struct cxl_event_header header;
union {
struct cxl_event_afu_interrupt irq;
struct cxl_event_data_storage fault;
struct cxl_event_afu_error afu_err;
};
};
cheers