fwctl: FWCTL_INFO to return basic information about the device

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.

Link: https://patch.msgid.link/r/3-v5-642aa0c94070+4447f-fwctl_jgg@nvidia.com
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
Tested-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

1 files changed, 55 insertions, 0 deletions

diff --git a/drivers/fwctl/main.c b/drivers/fwctl/main.c
index 4bba6109712e..bd84c4e5b3b9 100644
--- a/drivers/fwctl/main.c
+++ b/drivers/fwctl/main.c
@@ -27,8 +27,62 @@ 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 (!fwctl->ops->info && cmd->device_data_len) {
+		if (clear_user(u64_to_user_ptr(cmd->out_device_data),
+			       cmd->device_data_len))
+			return -EFAULT;
+	} else 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 fwctl_ucmd_buffer {
+	struct fwctl_info info;
 };
 
 struct fwctl_ioctl_op {
@@ -48,6 +102,7 @@ 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,