scsi: cxlflash: Introduce host ioctl support

As staging for supporting various host management functions, add a host
ioctl infrastructure to filter ioctl commands and perform operations that
are common for all host ioctls. Also update the cxlflash documentation to
create a new section for documenting host ioctls.
Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Documentation/ioctl/ioctl-number.txt

@@ -326,7 +326,7 @@ Code  Seq#(hex)	Include File		Comments
 0xB5	00-0F	uapi/linux/rpmsg.h	<mailto:linux-remoteproc@vger.kernel.org>
 0xC0	00-0F	linux/usb/iowarrior.h
 0xCA	00-0F	uapi/misc/cxl.h
-0xCA	80-8F	uapi/scsi/cxlflash_ioctl.h
+0xCA	80-BF	uapi/scsi/cxlflash_ioctl.h
 0xCB	00-1F	CBM serial IEC bus	in development:
 					<mailto:michael.klein@puffin.lb.shuttle.de>
 0xCD	01	linux/reiserfs_fs.h

Documentation/powerpc/cxlflash.txt

@@ -124,8 +124,8 @@ Block library API
     http://github.com/open-power/capiflash
 
 
-CXL Flash Driver IOCTLs
-=======================
+CXL Flash Driver LUN IOCTLs
+===========================
 
     Users, such as the block library, that wish to interface with a flash
     device (LUN) via user space access need to use the services provided
@@ -367,3 +367,18 @@ DK_CXLFLASH_MANAGE_LUN
     exclusive user space access (superpipe). In case a LUN is visible
     across multiple ports and adapters, this ioctl is used to uniquely
     identify each LUN by its World Wide Node Name (WWNN).
+
+
+CXL Flash Driver Host IOCTLs
+============================
+
+    Each host adapter instance that is supported by the cxlflash driver
+    has a special character device associated with it to enable a set of
+    host management function. These character devices are hosted in a
+    class dedicated for cxlflash and can be accessed via /dev/cxlflash/*.
+
+    Applications can be written to perform various functions using the
+    host ioctl APIs below.
+
+    The structure definitions for these IOCTLs are available in:
+    uapi/scsi/cxlflash_ioctl.h

drivers/scsi/cxlflash/main.c

@@ -2693,7 +2693,14 @@ static ssize_t lun_mode_store(struct device *dev,
 static ssize_t ioctl_version_show(struct device *dev,
 				  struct device_attribute *attr, char *buf)
 {
-	return scnprintf(buf, PAGE_SIZE, "%u\n", DK_CXLFLASH_VERSION_0);
+	ssize_t bytes = 0;
+
+	bytes = scnprintf(buf, PAGE_SIZE,
+			  "disk: %u\n", DK_CXLFLASH_VERSION_0);
+	bytes += scnprintf(buf + bytes, PAGE_SIZE - bytes,
+			   "host: %u\n", HT_CXLFLASH_VERSION_0);
+
+	return bytes;
 }
 
 /**
@@ -3211,12 +3218,124 @@ static int cxlflash_chr_open(struct inode *inode, struct file *file)
 	return 0;
 }
 
+/**
+ * decode_hioctl() - translates encoded host ioctl to easily identifiable string
+ * @cmd:        The host ioctl command to decode.
+ *
+ * Return: A string identifying the decoded host ioctl.
+ */
+static char *decode_hioctl(int cmd)
+{
+	switch (cmd) {
+	default:
+		return "UNKNOWN";
+	}
+
+	return "UNKNOWN";
+}
+
+/**
+ * cxlflash_chr_ioctl() - character device IOCTL handler
+ * @file:	File pointer for this device.
+ * @cmd:	IOCTL command.
+ * @arg:	Userspace ioctl data structure.
+ *
+ * A read/write semaphore is used to implement a 'drain' of currently
+ * running ioctls. The read semaphore is taken at the beginning of each
+ * ioctl thread and released upon concluding execution. Additionally the
+ * semaphore should be released and then reacquired in any ioctl execution
+ * path which will wait for an event to occur that is outside the scope of
+ * the ioctl (i.e. an adapter reset). To drain the ioctls currently running,
+ * a thread simply needs to acquire the write semaphore.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static long cxlflash_chr_ioctl(struct file *file, unsigned int cmd,
+			       unsigned long arg)
+{
+	typedef int (*hioctl) (struct cxlflash_cfg *, void *);
+
+	struct cxlflash_cfg *cfg = file->private_data;
+	struct device *dev = &cfg->dev->dev;
+	char buf[sizeof(union cxlflash_ht_ioctls)];
+	void __user *uarg = (void __user *)arg;
+	struct ht_cxlflash_hdr *hdr;
+	size_t size = 0;
+	bool known_ioctl = false;
+	int idx = 0;
+	int rc = 0;
+	hioctl do_ioctl = NULL;
+
+	static const struct {
+		size_t size;
+		hioctl ioctl;
+	} ioctl_tbl[] = {	/* NOTE: order matters here */
+	};
+
+	/* Hold read semaphore so we can drain if needed */
+	down_read(&cfg->ioctl_rwsem);
+
+	dev_dbg(dev, "%s: cmd=%u idx=%d tbl_size=%lu\n",
+		__func__, cmd, idx, sizeof(ioctl_tbl));
+
+	switch (cmd) {
+	default:
+		rc = -EINVAL;
+		goto out;
+	}
+
+	if (unlikely(copy_from_user(&buf, uarg, size))) {
+		dev_err(dev, "%s: copy_from_user() fail "
+			"size=%lu cmd=%d (%s) uarg=%p\n",
+			__func__, size, cmd, decode_hioctl(cmd), uarg);
+		rc = -EFAULT;
+		goto out;
+	}
+
+	hdr = (struct ht_cxlflash_hdr *)&buf;
+	if (hdr->version != HT_CXLFLASH_VERSION_0) {
+		dev_dbg(dev, "%s: Version %u not supported for %s\n",
+			__func__, hdr->version, decode_hioctl(cmd));
+		rc = -EINVAL;
+		goto out;
+	}
+
+	if (hdr->rsvd[0] || hdr->rsvd[1] || hdr->return_flags) {
+		dev_dbg(dev, "%s: Reserved/rflags populated\n", __func__);
+		rc = -EINVAL;
+		goto out;
+	}
+
+	rc = do_ioctl(cfg, (void *)&buf);
+	if (likely(!rc))
+		if (unlikely(copy_to_user(uarg, &buf, size))) {
+			dev_err(dev, "%s: copy_to_user() fail "
+				"size=%lu cmd=%d (%s) uarg=%p\n",
+				__func__, size, cmd, decode_hioctl(cmd), uarg);
+			rc = -EFAULT;
+		}
+
+	/* fall through to exit */
+
+out:
+	up_read(&cfg->ioctl_rwsem);
+	if (unlikely(rc && known_ioctl))
+		dev_err(dev, "%s: ioctl %s (%08X) returned rc=%d\n",
+			__func__, decode_hioctl(cmd), cmd, rc);
+	else
+		dev_dbg(dev, "%s: ioctl %s (%08X) returned rc=%d\n",
+			__func__, decode_hioctl(cmd), cmd, rc);
+	return rc;
+}
+
 /*
  * Character device file operations
  */
 static const struct file_operations cxlflash_chr_fops = {
 	.owner          = THIS_MODULE,
 	.open           = cxlflash_chr_open,
+	.unlocked_ioctl	= cxlflash_chr_ioctl,
+	.compat_ioctl	= cxlflash_chr_ioctl,
 };
 
 /**

include/uapi/scsi/cxlflash_ioctl.h

@@ -31,7 +31,7 @@ struct dk_cxlflash_hdr {
 };
 
 /*
- * Return flag definitions available to all ioctls
+ * Return flag definitions available to all superpipe ioctls
  *
  * Similar to the input flags, these are grown from the bottom-up with the
  * intention that ioctl-specific return flag definitions would grow from the
@@ -180,6 +180,10 @@ union cxlflash_ioctls {
 #define CXL_MAGIC 0xCA
 #define CXL_IOWR(_n, _s)	_IOWR(CXL_MAGIC, _n, struct _s)
 
+/*
+ * CXL Flash superpipe ioctls start at base of the reserved CXL_MAGIC
+ * region (0x80) and grow upwards.
+ */
 #define DK_CXLFLASH_ATTACH		CXL_IOWR(0x80, dk_cxlflash_attach)
 #define DK_CXLFLASH_USER_DIRECT		CXL_IOWR(0x81, dk_cxlflash_udirect)
 #define DK_CXLFLASH_RELEASE		CXL_IOWR(0x82, dk_cxlflash_release)
@@ -191,4 +195,29 @@ union cxlflash_ioctls {
 #define DK_CXLFLASH_VLUN_RESIZE		CXL_IOWR(0x88, dk_cxlflash_resize)
 #define DK_CXLFLASH_VLUN_CLONE		CXL_IOWR(0x89, dk_cxlflash_clone)
 
+/*
+ * Structure and flag definitions CXL Flash host ioctls
+ */
+
+#define HT_CXLFLASH_VERSION_0  0
+
+struct ht_cxlflash_hdr {
+	__u16 version;                  /* Version data */
+	__u16 subcmd;                   /* Sub-command */
+	__u16 rsvd[2];                  /* Reserved for future use */
+	__u64 flags;                    /* Input flags */
+	__u64 return_flags;             /* Returned flags */
+};
+
+union cxlflash_ht_ioctls {
+};
+
+#define MAX_HT_CXLFLASH_IOCTL_SZ	(sizeof(union cxlflash_ht_ioctls))
+
+/*
+ * CXL Flash host ioctls start at the top of the reserved CXL_MAGIC
+ * region (0xBF) and grow downwards.
+ */
+
+
 #endif /* ifndef _CXLFLASH_IOCTL_H */