[PATCH v3 03/10] fwctl: FWCTL_INFO to return basic information about the device

Jason Gunthorpe
2024-08-21T18:11:21Z

Userspace will need to know some details about the fwctl interface being
used to locate the correct userspace code to communicate with the
kernel. Provide a simple device_type enum indicating what the kernel
driver is.

Allow the device to provide a device specific info struct that contains
any additional information that the driver may need to provide to
userspace.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/fwctl/main.c | 51 ++++++++++++++++++++++++++++++++++++++
include/linux/fwctl.h | 12 +++++++++
include/uapi/fwctl/fwctl.h | 32 ++++++++++++++++++++++++
3 files changed, 95 insertions(+)

diff --git a/drivers/fwctl/main.c b/drivers/fwctl/main.c
index f2e30ffc1e0cb5..b281ccc52b4e57 100644
--- a/drivers/fwctl/main.c
+++ b/drivers/fwctl/main.c
@@ -25,8 +25,58 @@ struct fwctl_ucmd {
u32 user_size;
};

+static int ucmd_respond(struct fwctl_ucmd *ucmd, size_t cmd_len)
+{
+ if (copy_to_user(ucmd->ubuffer, ucmd->cmd,
+ min_t(size_t, ucmd->user_size, cmd_len)))
+ return -EFAULT;
+ return 0;
+}
+
+static int copy_to_user_zero_pad(void __user *to, const void *from,
+ size_t from_len, size_t user_len)
+{
+ size_t copy_len;
+
+ copy_len = min(from_len, user_len);
+ if (copy_to_user(to, from, copy_len))
+ return -EFAULT;
+ if (copy_len < user_len) {
+ if (clear_user(to + copy_len, user_len - copy_len))
+ return -EFAULT;
+ }
+ return 0;
+}
+
+static int fwctl_cmd_info(struct fwctl_ucmd *ucmd)
+{
+ struct fwctl_device *fwctl = ucmd->uctx->fwctl;
+ struct fwctl_info *cmd = ucmd->cmd;
+ size_t driver_info_len = 0;
+
+ if (cmd->flags)
+ return -EOPNOTSUPP;
+
+ if (cmd->device_data_len) {
+ void *driver_info __free(kfree) =
+ fwctl->ops->info(ucmd->uctx, &driver_info_len);
+ if (IS_ERR(driver_info))
+ return PTR_ERR(driver_info);
+
+ if (copy_to_user_zero_pad(u64_to_user_ptr(cmd->out_device_data),
+ driver_info, driver_info_len,
+ cmd->device_data_len))
+ return -EFAULT;
+ }
+
+ cmd->out_device_type = fwctl->ops->device_type;
+ cmd->device_data_len = driver_info_len;
+ return ucmd_respond(ucmd, sizeof(*cmd));
+}
+
/* On stack memory for the ioctl structs */
union ucmd_buffer {
+ struct fwctl_info info;
};

struct fwctl_ioctl_op {
@@ -46,6 +96,7 @@ struct fwctl_ioctl_op {
.execute = _fn, \
}
static const struct fwctl_ioctl_op fwctl_ioctl_ops[] = {
+ IOCTL_OP(FWCTL_INFO, fwctl_cmd_info, struct fwctl_info, out_device_data),
};

static long fwctl_fops_ioctl(struct file *filp, unsigned int cmd,
diff --git a/include/linux/fwctl.h b/include/linux/fwctl.h
index ca4245825e91bf..6b596931a55169 100644
--- a/include/linux/fwctl.h
+++ b/include/linux/fwctl.h
@@ -7,6 +7,7 @@
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/cleanup.h>
+#include <uapi/fwctl/fwctl.h>

struct fwctl_device;
struct fwctl_uctx;
@@ -19,6 +20,10 @@ struct fwctl_uctx;
* it will block device hot unplug and module unloading.
*/
struct fwctl_ops {
+ /**
+ * @device_type: The drivers assigned device_type number. This is uABI.
+ */
+ enum fwctl_device_type device_type;
/**
* @uctx_size: The size of the fwctl_uctx struct to allocate. The first
* bytes of this memory will be a fwctl_uctx. The driver can use the
@@ -35,6 +40,13 @@ struct fwctl_ops {
* is closed.
*/
void (*close_uctx)(struct fwctl_uctx *uctx);
+ /**
+ * @info: Implement FWCTL_INFO. Return a kmalloc() memory that is copied
+ * to out_device_data. On input length indicates the size of the user
+ * buffer on output it indicates the size of the memory. The driver can
+ * ignore length on input, the core code will handle everything.
+ */
+ void *(*info)(struct fwctl_uctx *uctx, size_t *length);
};

/**
diff --git a/include/uapi/fwctl/fwctl.h b/include/uapi/fwctl/fwctl.h
index 22fa750d7e8184..39db9f09f8068e 100644
--- a/include/uapi/fwctl/fwctl.h
+++ b/include/uapi/fwctl/fwctl.h
@@ -4,6 +4,9 @@
#ifndef _UAPI_FWCTL_H
#define _UAPI_FWCTL_H

+#include <linux/types.h>
+#include <linux/ioctl.h>
+
#define FWCTL_TYPE 0x9A

/**
@@ -33,6 +36,35 @@
*/
enum {
FWCTL_CMD_BASE = 0,
+ FWCTL_CMD_INFO = 0,
+ FWCTL_CMD_RPC = 1,
};

+enum fwctl_device_type {
+ FWCTL_DEVICE_TYPE_ERROR = 0,
+};
+
+/**
+ * struct fwctl_info - ioctl(FWCTL_INFO)
+ * @size: sizeof(struct fwctl_info)
+ * @flags: Must be 0
+ * @out_device_type: Returns the type of the device from enum fwctl_device_type
+ * @device_data_len: On input the length of the out_device_data memory. On
+ * output the size of the kernel's device_data which may be larger or
+ * smaller than the input. Maybe 0 on input.
+ * @out_device_data: Pointer to a memory of device_data_len bytes. Kernel will
+ * fill the entire memory, zeroing as required.
+ *
+ * Returns basic information about this fwctl instance, particularly what driver
+ * is being used to define the device_data format.
+ */
+struct fwctl_info {
+ __u32 size;
+ __u32 flags;
+ __u32 out_device_type;
+ __u32 device_data_len;
+ __aligned_u64 out_device_data;
+};
+#define FWCTL_INFO _IO(FWCTL_TYPE, FWCTL_CMD_INFO)
+
#endif
--
2.46.0