[PATCH V3 1/2] devicetree/bindings: Add binding for operator panel on FSP machines

[PATCH V3 1/2] devicetree/bindings: Add binding for operator panel on FSP machines

[Suraj Jitindar Singh]

Add a binding to Documentation/devicetree/bindings/powerpc/opal
(oppanel-opal.txt) for the operator panel which is present on IBM
Power Systems machines with FSPs.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Stewart Smith <stewart@linux.vnet.ibm.com>

---

Change Log:

V1 -> V2:
	- Nothing
V2 -> V3:
	- Change "IBM pseries machines" to "IBM Power Systems machines"
	in the commit message for improved clarity.
---
 .../devicetree/bindings/powerpc/opal/oppanel-opal.txt      | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/powerpc/opal/oppanel-opal.txt

diff --git a/Documentation/devicetree/bindings/powerpc/opal/oppanel-opal.txt b/Documentation/devicetree/bindings/powerpc/opal/oppanel-opal.txt
new file mode 100644
index 0000000..dffb791
--- /dev/null
+++ b/Documentation/devicetree/bindings/powerpc/opal/oppanel-opal.txt
@@ -0,0 +1,14 @@
+IBM OPAL Operator Panel Binding
+-------------------------------
+
+Required properties:
+- compatible : Should be "ibm,opal-oppanel".
+- #lines     : Number of lines on the operator panel e.g. <0x2>.
+- #length    : Number of characters per line of the operator panel e.g. <0x10>.
+
+Example:
+	oppanel {
+		compatible = "ibm,opal-oppanel";
+		#lines = <0x2>;
+		#length = <0x10>;
+	};
-- 
2.5.0

[PATCH V3 2/2] powerpc/drivers: Add driver for operator panel on FSP machines

[Suraj Jitindar Singh]

Implement new character device driver to allow access from user space
to the 2x16 character operator panel display present on IBM Power Systems
machines with FSPs.

This will allow status information to be presented on the display which
is visible to a user.

The driver implements a 32 character buffer which a user can read/write
by accessing the device (/dev/oppanel). This buffer is then displayed on
the operator panel display. Any attempt to write past the 32nd position
will have no effect and attempts to write more than 32 characters will be
truncated. The device may only be accessed by a single process at a time.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>

---

Change Log:

V1 -> V2:
	- Replace "IBM pSeries machines" with "IBM Power Systems machines
	with FSPs" for improved clarity
	- Basic wording/grammar fixes
V2 -> V3:
	- Nothing
---
 MAINTAINERS                                    |   6 +
 arch/powerpc/configs/powernv_defconfig         |   1 +
 arch/powerpc/include/asm/opal.h                |   2 +
 arch/powerpc/platforms/powernv/opal-wrappers.S |   1 +
 arch/powerpc/platforms/powernv/opal.c          |   5 +
 drivers/char/Kconfig                           |  14 ++
 drivers/char/Makefile                          |   1 +
 drivers/char/op-panel-powernv.c                | 247 +++++++++++++++++++++++++
 8 files changed, 277 insertions(+)
 create mode 100644 drivers/char/op-panel-powernv.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 40eb1db..dbacb12 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8817,6 +8817,12 @@ F:	drivers/firmware/psci.c
 F:	include/linux/psci.h
 F:	include/uapi/linux/psci.h
 
+POWERNV OPERATOR PANEL LCD DISPLAY DRIVER
+M:	Suraj Jitindar Singh <sjitindarsingh@gmail.com>
+L:	linuxppc-dev@lists.ozlabs.org
+S:	Maintained
+F:	drivers/char/op-panel-powernv.c
+
 PNP SUPPORT
 M:	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
 S:	Maintained
diff --git a/arch/powerpc/configs/powernv_defconfig b/arch/powerpc/configs/powernv_defconfig
index 0450310..8f9f4ce 100644
--- a/arch/powerpc/configs/powernv_defconfig
+++ b/arch/powerpc/configs/powernv_defconfig
@@ -181,6 +181,7 @@ CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_JSM=m
 CONFIG_VIRTIO_CONSOLE=m
+CONFIG_IBM_OP_PANEL=m
 CONFIG_IPMI_HANDLER=y
 CONFIG_IPMI_DEVICE_INTERFACE=y
 CONFIG_IPMI_POWERNV=y
diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 9d86c66..b33e349 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -178,6 +178,8 @@ int64_t opal_dump_ack(uint32_t dump_id);
 int64_t opal_dump_resend_notification(void);
 
 int64_t opal_get_msg(uint64_t buffer, uint64_t size);
+int64_t opal_write_oppanel_async(uint64_t token, oppanel_line_t *lines,
+					uint64_t num_lines);
 int64_t opal_check_completion(uint64_t buffer, uint64_t size, uint64_t token);
 int64_t opal_sync_host_reboot(void);
 int64_t opal_get_param(uint64_t token, uint32_t param_id, uint64_t buffer,
diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
index e45b88a..ddba8bf 100644
--- a/arch/powerpc/platforms/powernv/opal-wrappers.S
+++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
@@ -278,6 +278,7 @@ OPAL_CALL(opal_dump_info2,			OPAL_DUMP_INFO2);
 OPAL_CALL(opal_dump_read,			OPAL_DUMP_READ);
 OPAL_CALL(opal_dump_ack,			OPAL_DUMP_ACK);
 OPAL_CALL(opal_get_msg,				OPAL_GET_MSG);
+OPAL_CALL(opal_write_oppanel_async,		OPAL_WRITE_OPPANEL_ASYNC);
 OPAL_CALL(opal_check_completion,		OPAL_CHECK_ASYNC_COMPLETION);
 OPAL_CALL(opal_dump_resend_notification,	OPAL_DUMP_RESEND);
 OPAL_CALL(opal_sync_host_reboot,		OPAL_SYNC_HOST_REBOOT);
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 0256d07..228751a 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -751,6 +751,9 @@ static int __init opal_init(void)
 	opal_pdev_init(opal_node, "ibm,opal-flash");
 	opal_pdev_init(opal_node, "ibm,opal-prd");
 
+	/* Initialise platform device: oppanel interface */
+	opal_pdev_init(opal_node, "ibm,opal-oppanel");
+
 	/* Initialise OPAL kmsg dumper for flushing console on panic */
 	opal_kmsg_init();
 
@@ -885,3 +888,5 @@ EXPORT_SYMBOL_GPL(opal_i2c_request);
 /* Export these symbols for PowerNV LED class driver */
 EXPORT_SYMBOL_GPL(opal_leds_get_ind);
 EXPORT_SYMBOL_GPL(opal_leds_set_ind);
+/* Export this symbol for PowerNV Operator Panel class driver */
+EXPORT_SYMBOL_GPL(opal_write_oppanel_async);
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 3ec0766..c1d354d 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -178,6 +178,20 @@ config IBM_BSR
 	  of threads across a large system which avoids bouncing a cacheline
 	  between several cores on a system
 
+config IBM_OP_PANEL
+	tristate "IBM POWER Operator Panel Display support"
+	depends on PPC_POWERNV
+	default m
+	help
+	  If you say Y here, a special character device node, /dev/oppanel,
+	  will be created which exposes the operator panel display on IBM
+	  Power Systems machines with FSPs.
+
+	  If you don't require access to the operator panel display from user
+	  space, say N.
+
+	  If unsure, say M here to build it as a module called op-panel-powernv.
+
 source "drivers/char/ipmi/Kconfig"
 
 config DS1620
diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index d8a7579..a02c61b 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -60,3 +60,4 @@ js-rtc-y = rtc.o
 
 obj-$(CONFIG_TILE_SROM)		+= tile-srom.o
 obj-$(CONFIG_XILLYBUS)		+= xillybus/
+obj-$(CONFIG_IBM_OP_PANEL)	+= op-panel-powernv.o
diff --git a/drivers/char/op-panel-powernv.c b/drivers/char/op-panel-powernv.c
new file mode 100644
index 0000000..90b74b7
--- /dev/null
+++ b/drivers/char/op-panel-powernv.c
@@ -0,0 +1,247 @@
+/*
+ * OPAL Operator Panel Display Driver
+ *
+ * (C) Copyright IBM Corp. 2016
+ *
+ * Author: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/platform_device.h>
+#include <linux/miscdevice.h>
+
+#include <asm/opal.h>
+#include <asm/opal-api.h>
+
+/*
+ * This driver creates a character device (/dev/oppanel) which exposes the
+ * operator panel (2x16 character LCD display) on IBM Power Systems machines
+ * with FSPs.
+ * A 32 character buffer written to the device will be displayed on the
+ * operator panel.
+ */
+
+static DEFINE_MUTEX(oppanel_mutex);
+
+static oppanel_line_t	*oppanel_lines;
+static char		*oppanel_data;
+static u32		line_length, num_lines;
+
+static loff_t oppanel_llseek(struct file *filp, loff_t offset, int whence)
+{
+	return fixed_size_llseek(filp, offset, whence, num_lines *
+		line_length);
+}
+
+static ssize_t oppanel_read(struct file *filp, char __user *userbuf, size_t len,
+		loff_t *f_pos)
+{
+	return simple_read_from_buffer(userbuf, len, f_pos, oppanel_data,
+		(num_lines * line_length));
+}
+
+static int __op_panel_write(void)
+{
+	int rc, token;
+	struct opal_msg msg;
+
+	token = opal_async_get_token_interruptible();
+	if (token < 0) {
+		if (token != -ERESTARTSYS)
+			pr_err("Couldn't get OPAL async token [token=%d]\n",
+				token);
+		return token;
+	}
+
+	rc = opal_write_oppanel_async(token, oppanel_lines, (u64) num_lines);
+	switch (rc) {
+	case OPAL_ASYNC_COMPLETION:
+		rc = opal_async_wait_response(token, &msg);
+		if (rc) {
+			pr_err("Failed to wait for async response [rc=%d]\n",
+				rc);
+			goto out_token;
+		}
+		rc = be64_to_cpu(msg.params[1]);
+		if (rc != OPAL_SUCCESS) {
+			pr_err("OPAL async call returned failed [rc=%d]\n", rc);
+			goto out_token;
+		}
+	case OPAL_SUCCESS:
+		break;
+	default:
+		pr_err("OPAL write op-panel call failed [rc=%d]\n", rc);
+	}
+
+out_token:
+	opal_async_release_token(token);
+	return rc;
+}
+
+static ssize_t oppanel_write(struct file *filp, const char __user *userbuf,
+		size_t len, loff_t *f_pos)
+{
+	ssize_t ret;
+	loff_t f_pos_prev = *f_pos;
+	int rc;
+
+	if (*f_pos >= (num_lines * line_length))
+		return -EFBIG;
+
+	ret = simple_write_to_buffer(oppanel_data, (num_lines *
+			line_length), f_pos, userbuf, len);
+	if (ret > 0) {
+		rc = __op_panel_write();
+		if (rc != OPAL_SUCCESS) {
+			pr_err("OPAL call failed to write to op panel display [rc=%d]\n",
+				rc);
+			*f_pos = f_pos_prev;
+			return -EIO;
+		}
+	}
+	return ret;
+}
+
+static int oppanel_open(struct inode *inode, struct file *filp)
+{
+	if (!mutex_trylock(&oppanel_mutex)) {
+		pr_debug("Device Busy\n");
+		return -EBUSY;
+	}
+	return 0;
+}
+
+static int oppanel_release(struct inode *inode, struct file *filp)
+{
+	mutex_unlock(&oppanel_mutex);
+	return 0;
+}
+
+static const struct file_operations oppanel_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= oppanel_llseek,
+	.read		= oppanel_read,
+	.write		= oppanel_write,
+	.open		= oppanel_open,
+	.release	= oppanel_release
+};
+
+static struct miscdevice oppanel_dev = {
+	.minor		= MISC_DYNAMIC_MINOR,
+	.name		= "oppanel",
+	.fops		= &oppanel_fops
+};
+
+static int oppanel_probe(struct platform_device *pdev)
+{
+	int rc, i;
+	struct device_node *dev_node = pdev->dev.of_node;
+	const u32 *length_val, *lines_val;
+
+	if (strncmp(dev_node->name, "oppanel", 7)) {
+		pr_err("Operator panel not found\n");
+		return -1;
+	}
+
+	length_val = of_get_property(dev_node, "#length", NULL);
+	if (!length_val) {
+		pr_err("Operator panel length property not found\n");
+		return -1;
+	}
+	line_length = be32_to_cpu(*length_val);
+	lines_val = of_get_property(dev_node, "#lines", NULL);
+	if (!lines_val) {
+		pr_err("Operator panel lines property not found\n");
+		return -1;
+	}
+	num_lines = be32_to_cpu(*lines_val);
+
+	pr_debug("Operator panel found with %u lines of length %u\n",
+			num_lines, line_length);
+
+	oppanel_data = kcalloc((num_lines * line_length), sizeof(char),
+		GFP_KERNEL);
+	if (!oppanel_data)
+		return -ENOMEM;
+
+	oppanel_lines = kcalloc(num_lines, sizeof(oppanel_line_t), GFP_KERNEL);
+	if (!oppanel_lines) {
+		kfree(oppanel_data);
+		return -ENOMEM;
+	}
+
+	memset(oppanel_data, ' ', (num_lines * line_length));
+	for (i = 0; i < num_lines; i++) {
+		oppanel_lines[i].line_len = cpu_to_be64((u64) line_length);
+		oppanel_lines[i].line = cpu_to_be64((u64) &oppanel_data[i *
+						line_length]);
+	}
+
+	mutex_init(&oppanel_mutex);
+
+	rc = misc_register(&oppanel_dev);
+	if (rc) {
+		pr_err("Failed to register as misc device\n");
+		goto remove_mutex;
+	}
+
+	pr_info("Device Successfully Initialised\n");
+	return 0;
+
+remove_mutex:
+	mutex_destroy(&oppanel_mutex);
+	kfree(oppanel_lines);
+	kfree(oppanel_data);
+	return rc;
+}
+
+static int oppanel_remove(struct platform_device *pdev)
+{
+	misc_deregister(&oppanel_dev);
+	mutex_destroy(&oppanel_mutex);
+	kfree(oppanel_lines);
+	kfree(oppanel_data);
+	pr_info("Device Successfully Removed\n");
+	return 0;
+}
+
+static const struct of_device_id oppanel_match[] = {
+	{ .compatible = "ibm,opal-oppanel" },
+	{ },
+};
+
+static struct platform_driver oppanel_driver = {
+	.driver	= {
+		.name		= "op-panel-powernv",
+		.of_match_table	= oppanel_match,
+	},
+	.probe	= oppanel_probe,
+	.remove	= oppanel_remove,
+};
+
+module_platform_driver(oppanel_driver);
+
+MODULE_DEVICE_TABLE(of, oppanel_match);
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("PowerNV Operator Panel LCD Display Driver");
+MODULE_AUTHOR("Suraj Jitindar Singh <sjitindarsingh@gmail.com>");
-- 
2.5.0

Re: [V3, 2/2] powerpc/drivers: Add driver for operator panel on FSP machines

[Michael Ellerman]

On Thu, 2016-28-04 at 07:02:38 UTC, Suraj Jitindar Singh wrote:
> Implement new character device driver to allow access from user space
> to the 2x16 character operator panel display present on IBM Power Systems
> machines with FSPs.

I looked at this previously and somehow convinced myself it depended on skiboot
changes, but it seems it doesn't.

Some comments below ...

> This will allow status information to be presented on the display which
> is visible to a user.
> 
> The driver implements a 32 character buffer which a user can read/write

It looks like "32" is actually just one possible size, it comes from the device
tree no?

> by accessing the device (/dev/oppanel). This buffer is then displayed on

Are we sure "op_panel" wouldn't be better?

> diff --git a/arch/powerpc/configs/powernv_defconfig b/arch/powerpc/configs/powernv_defconfig
> index 0450310..8f9f4ce 100644
> --- a/arch/powerpc/configs/powernv_defconfig
> +++ b/arch/powerpc/configs/powernv_defconfig
> @@ -181,6 +181,7 @@ CONFIG_SERIAL_8250=y
>  CONFIG_SERIAL_8250_CONSOLE=y
>  CONFIG_SERIAL_JSM=m
>  CONFIG_VIRTIO_CONSOLE=m
> +CONFIG_IBM_OP_PANEL=m

I think CONFIG_POWERNV_OP_PANEL would be a better name.

> diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
> index 9d86c66..b33e349 100644
> --- a/arch/powerpc/include/asm/opal.h
> +++ b/arch/powerpc/include/asm/opal.h
> @@ -178,6 +178,8 @@ int64_t opal_dump_ack(uint32_t dump_id);
>  int64_t opal_dump_resend_notification(void);
>  
>  int64_t opal_get_msg(uint64_t buffer, uint64_t size);
> +int64_t opal_write_oppanel_async(uint64_t token, oppanel_line_t *lines,
> +					uint64_t num_lines);

I realise you're just following the skiboot code which uses oppanel_line_t, but
please don't do that in the kernel. Just use struct oppanel_line directly.

> diff --git a/drivers/char/Makefile b/drivers/char/Makefile
> index d8a7579..a02c61b 100644
> --- a/drivers/char/Makefile
> +++ b/drivers/char/Makefile
> @@ -60,3 +60,4 @@ js-rtc-y = rtc.o
>  
>  obj-$(CONFIG_TILE_SROM)		+= tile-srom.o
>  obj-$(CONFIG_XILLYBUS)		+= xillybus/
> +obj-$(CONFIG_IBM_OP_PANEL)	+= op-panel-powernv.o

I'd prefer powernv-op-panel.c, but up to you.

> diff --git a/drivers/char/op-panel-powernv.c b/drivers/char/op-panel-powernv.c
> new file mode 100644
> index 0000000..90b74b7
> --- /dev/null
> +++ b/drivers/char/op-panel-powernv.c
> @@ -0,0 +1,247 @@
> +/*
> + * OPAL Operator Panel Display Driver
> + *
> + * (C) Copyright IBM Corp. 2016
> + *
> + * Author: Suraj Jitindar Singh <sjitindarsingh@gmail.com>

I'm not a fan of email addresses in C files, they just bit rot.

The preferred format is:

 * Copyright 2016, Suraj Jitindar Singh, IBM Corporation.

> + *
> + * 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.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.

We don't need that paragraph in every file.

> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/fs.h>
> +#include <linux/device.h>
> +#include <linux/errno.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/slab.h>
> +#include <linux/platform_device.h>
> +#include <linux/miscdevice.h>
> +
> +#include <asm/opal.h>
> +#include <asm/opal-api.h>

opal-api.h is sort of an implementation detail, you should just include opal.h

> +/*
> + * This driver creates a character device (/dev/oppanel) which exposes the
> + * operator panel (2x16 character LCD display) on IBM Power Systems machines
> + * with FSPs.
> + * A 32 character buffer written to the device will be displayed on the
> + * operator panel.
> + */
> +
> +static DEFINE_MUTEX(oppanel_mutex);
> +
> +static oppanel_line_t	*oppanel_lines;
> +static char		*oppanel_data;
> +static u32		line_length, num_lines;

You calculate (num_lines * line_length) a lot, that would probably be worth
storing as eg. "oppanel_size" or something.

> +
> +static loff_t oppanel_llseek(struct file *filp, loff_t offset, int whence)
> +{
> +	return fixed_size_llseek(filp, offset, whence, num_lines *
> +		line_length);

I don't think you need to wrap that line?

> +}
> +
> +static ssize_t oppanel_read(struct file *filp, char __user *userbuf, size_t len,
> +		loff_t *f_pos)

I prefer to align the second line unless the signature is ridiculously wide:

static ssize_t oppanel_read(struct file *filp, char __user *userbuf, size_t len,
			    loff_t *f_pos)

> +{
> +	return simple_read_from_buffer(userbuf, len, f_pos, oppanel_data,
> +		(num_lines * line_length));
> +}
> +
> +static int __op_panel_write(void)

Can you think of a better name for this?

> +{
> +	int rc, token;
> +	struct opal_msg msg;
> +
> +	token = opal_async_get_token_interruptible();
> +	if (token < 0) {
> +		if (token != -ERESTARTSYS)
> +			pr_err("Couldn't get OPAL async token [token=%d]\n",
> +				token);
> +		return token;
> +	}
> +
> +	rc = opal_write_oppanel_async(token, oppanel_lines, (u64) num_lines);

I don't think you need the cast?

> +	switch (rc) {
> +	case OPAL_ASYNC_COMPLETION:
> +		rc = opal_async_wait_response(token, &msg);
> +		if (rc) {
> +			pr_err("Failed to wait for async response [rc=%d]\n",
> +				rc);
> +			goto out_token;
> +		}
> +		rc = be64_to_cpu(msg.params[1]);

Is params[1] documented somewhere? Seems like a helper might be nice.

> +		if (rc != OPAL_SUCCESS) {
> +			pr_err("OPAL async call returned failed [rc=%d]\n", rc);
> +			goto out_token;

You don't need the goto do you? You can just break?

> +		}
> +	case OPAL_SUCCESS:
> +		break;
> +	default:
> +		pr_err("OPAL write op-panel call failed [rc=%d]\n", rc);

This and the other pr_err()s should be ratelimited, or become pr_debug().

> +	}
> +
> +out_token:
> +	opal_async_release_token(token);
> +	return rc;
> +}
> +
> +static ssize_t oppanel_write(struct file *filp, const char __user *userbuf,
> +		size_t len, loff_t *f_pos)
> +{
> +	ssize_t ret;
> +	loff_t f_pos_prev = *f_pos;
> +	int rc;
> +
> +	if (*f_pos >= (num_lines * line_length))
> +		return -EFBIG;
> +
> +	ret = simple_write_to_buffer(oppanel_data, (num_lines *
> +			line_length), f_pos, userbuf, len);

AFAICS you never clear the buffer, so if I write "foobar" and then call write
again with "foo", I'll end up with "foobar" on the panel?

Should you clear the buffer when the first write comes in (f_pos == 0) ?

> +	if (ret > 0) {
> +		rc = __op_panel_write();
> +		if (rc != OPAL_SUCCESS) {
> +			pr_err("OPAL call failed to write to op panel display [rc=%d]\n",
> +				rc);
> +			*f_pos = f_pos_prev;
> +			return -EIO;
> +		}
> +	}
> +	return ret;
> +}
> +
> +static int oppanel_open(struct inode *inode, struct file *filp)
> +{
> +	if (!mutex_trylock(&oppanel_mutex)) {
> +		pr_debug("Device Busy\n");
> +		return -EBUSY;
> +	}
> +	return 0;
> +}
> +
> +static int oppanel_release(struct inode *inode, struct file *filp)
> +{
> +	mutex_unlock(&oppanel_mutex);
> +	return 0;
> +}
> +
> +static const struct file_operations oppanel_fops = {
> +	.owner		= THIS_MODULE,
> +	.llseek		= oppanel_llseek,
> +	.read		= oppanel_read,
> +	.write		= oppanel_write,
> +	.open		= oppanel_open,
> +	.release	= oppanel_release
> +};
> +
> +static struct miscdevice oppanel_dev = {
> +	.minor		= MISC_DYNAMIC_MINOR,
> +	.name		= "oppanel",
> +	.fops		= &oppanel_fops
> +};
> +
> +static int oppanel_probe(struct platform_device *pdev)
> +{
> +	int rc, i;
> +	struct device_node *dev_node = pdev->dev.of_node;

dev_node should be called np.

> +	const u32 *length_val, *lines_val;

My preference is reverse Christmas tree style:

	const u32 *length_val, *lines_val;
	struct device_node *np;
	int rc, i;

	np = pdev->dev.of_node;

> +
> +	if (strncmp(dev_node->name, "oppanel", 7)) {

You are using a compatible check (via the match table) so you don't need that
check. Only checking the start of the name (7) would also be wrong.

> +		pr_err("Operator panel not found\n");
> +		return -1;
> +	}
> +
> +	length_val = of_get_property(dev_node, "#length", NULL);
> +	if (!length_val) {
> +		pr_err("Operator panel length property not found\n");
> +		return -1;
> +	}
> +	line_length = be32_to_cpu(*length_val);

Please use of_property_read_u32(), you shouldn't need any endian conversions in
this code.

> +	lines_val = of_get_property(dev_node, "#lines", NULL);
> +	if (!lines_val) {
> +		pr_err("Operator panel lines property not found\n");
> +		return -1;
> +	}
> +	num_lines = be32_to_cpu(*lines_val);

Ditto.

> +	pr_debug("Operator panel found with %u lines of length %u\n",
> +			num_lines, line_length);

pr_devel() would probably be even better (compiled out entirely).

> +	oppanel_data = kcalloc((num_lines * line_length), sizeof(char),
> +		GFP_KERNEL);
> +	if (!oppanel_data)
> +		return -ENOMEM;
> +
> +	oppanel_lines = kcalloc(num_lines, sizeof(oppanel_line_t), GFP_KERNEL);
> +	if (!oppanel_lines) {
> +		kfree(oppanel_data);
> +		return -ENOMEM;

That should be:
		rc = -ENOMEM;
		goto free_oppanel;

> +	}
> +
> +	memset(oppanel_data, ' ', (num_lines * line_length));
> +	for (i = 0; i < num_lines; i++) {
> +		oppanel_lines[i].line_len = cpu_to_be64((u64) line_length);
> +		oppanel_lines[i].line = cpu_to_be64((u64) &oppanel_data[i *
> +						line_length]);

We should be giving OPAL the real address of &oppanel_data[i * line_length],
which means you need to wrap it in __pa(). Unless that's happening somewhere
else I missed?

> +	}
> +
> +	mutex_init(&oppanel_mutex);

AFAIK you don't need to do that because you used DEFINE_MUTEX() above?

> +	rc = misc_register(&oppanel_dev);
> +	if (rc) {
> +		pr_err("Failed to register as misc device\n");
> +		goto remove_mutex;
> +	}
> +
> +	pr_info("Device Successfully Initialised\n");

We don't need a pr_info() on success.

> +	return 0;
> +
> +remove_mutex:
> +	mutex_destroy(&oppanel_mutex);
> +	kfree(oppanel_lines);
> +	kfree(oppanel_data);
> +	return rc;
> +}
> +
> +static int oppanel_remove(struct platform_device *pdev)
> +{
> +	misc_deregister(&oppanel_dev);
> +	mutex_destroy(&oppanel_mutex);
> +	kfree(oppanel_lines);
> +	kfree(oppanel_data);
> +	pr_info("Device Successfully Removed\n");

Don't need the pr_info().

cheers

Re: [V3, 2/2] powerpc/drivers: Add driver for operator panel on FSP machines

[Suraj Jitindar Singh]

On Thu, 16 Jun 2016 20:22:39 +1000 (AEST)
Michael Ellerman <mpe@ellerman.id.au> wrote:

> On Thu, 2016-28-04 at 07:02:38 UTC, Suraj Jitindar Singh wrote:
> > Implement new character device driver to allow access from user
> > space to the 2x16 character operator panel display present on IBM
> > Power Systems machines with FSPs.  
> 
> I looked at this previously and somehow convinced myself it depended
> on skiboot changes, but it seems it doesn't.
> 
> Some comments below ...
> 
> > This will allow status information to be presented on the display
> > which is visible to a user.
> > 
> > The driver implements a 32 character buffer which a user can
> > read/write  
> 
> It looks like "32" is actually just one possible size, it comes from
> the device tree no?
Correct, although it is kind of hard coded into skiboot at the moment. I
will change the commit message to omit this.
> 
> > by accessing the device (/dev/oppanel). This buffer is then
> > displayed on  
> 
> Are we sure "op_panel" wouldn't be better?
Seems like that will cause less confusion, will change it.
> 
> > diff --git a/arch/powerpc/configs/powernv_defconfig
> > b/arch/powerpc/configs/powernv_defconfig index 0450310..8f9f4ce
> > 100644 --- a/arch/powerpc/configs/powernv_defconfig
> > +++ b/arch/powerpc/configs/powernv_defconfig
> > @@ -181,6 +181,7 @@ CONFIG_SERIAL_8250=y
> >  CONFIG_SERIAL_8250_CONSOLE=y
> >  CONFIG_SERIAL_JSM=m
> >  CONFIG_VIRTIO_CONSOLE=m
> > +CONFIG_IBM_OP_PANEL=m  
> 
> I think CONFIG_POWERNV_OP_PANEL would be a better name.
I agree.
> 
> > diff --git a/arch/powerpc/include/asm/opal.h
> > b/arch/powerpc/include/asm/opal.h index 9d86c66..b33e349 100644
> > --- a/arch/powerpc/include/asm/opal.h
> > +++ b/arch/powerpc/include/asm/opal.h
> > @@ -178,6 +178,8 @@ int64_t opal_dump_ack(uint32_t dump_id);
> >  int64_t opal_dump_resend_notification(void);
> >  
> >  int64_t opal_get_msg(uint64_t buffer, uint64_t size);
> > +int64_t opal_write_oppanel_async(uint64_t token, oppanel_line_t
> > *lines,
> > +					uint64_t num_lines);  
> 
> I realise you're just following the skiboot code which uses
> oppanel_line_t, but please don't do that in the kernel. Just use
> struct oppanel_line directly.
Struct oppanel_line is typedefed to oppanel_line_t in opal-api.h,
so this should be oppanel_line_t or struct oppanel_line?
> 
> > diff --git a/drivers/char/Makefile b/drivers/char/Makefile
> > index d8a7579..a02c61b 100644
> > --- a/drivers/char/Makefile
> > +++ b/drivers/char/Makefile
> > @@ -60,3 +60,4 @@ js-rtc-y = rtc.o
> >  
> >  obj-$(CONFIG_TILE_SROM)		+= tile-srom.o
> >  obj-$(CONFIG_XILLYBUS)		+= xillybus/
> > +obj-$(CONFIG_IBM_OP_PANEL)	+= op-panel-powernv.o  
> 
> I'd prefer powernv-op-panel.c, but up to you.
This will align to the name of the config option, so will change
to your recommendation
> 
> > diff --git a/drivers/char/op-panel-powernv.c
> > b/drivers/char/op-panel-powernv.c new file mode 100644
> > index 0000000..90b74b7
> > --- /dev/null
> > +++ b/drivers/char/op-panel-powernv.c
> > @@ -0,0 +1,247 @@
> > +/*
> > + * OPAL Operator Panel Display Driver
> > + *
> > + * (C) Copyright IBM Corp. 2016
> > + *
> > + * Author: Suraj Jitindar Singh <sjitindarsingh@gmail.com>  
> 
> I'm not a fan of email addresses in C files, they just bit rot.
> 
> The preferred format is:
> 
>  * Copyright 2016, Suraj Jitindar Singh, IBM Corporation.
> 
> > + *
> > + * 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.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.  
> 
> We don't need that paragraph in every file.
> 
Will update and remove these sections.
> > + */
> > +
> > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > +
> > +#include <linux/init.h>
> > +#include <linux/module.h>
> > +#include <linux/kernel.h>
> > +#include <linux/fs.h>
> > +#include <linux/device.h>
> > +#include <linux/errno.h>
> > +#include <linux/mutex.h>
> > +#include <linux/of.h>
> > +#include <linux/slab.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/miscdevice.h>
> > +
> > +#include <asm/opal.h>
> > +#include <asm/opal-api.h>  
> 
> opal-api.h is sort of an implementation detail, you should just
> include opal.h
> 
> > +/*
> > + * This driver creates a character device (/dev/oppanel) which
> > exposes the
> > + * operator panel (2x16 character LCD display) on IBM Power
> > Systems machines
> > + * with FSPs.
> > + * A 32 character buffer written to the device will be displayed
> > on the
> > + * operator panel.
> > + */
> > +
> > +static DEFINE_MUTEX(oppanel_mutex);
> > +
> > +static oppanel_line_t	*oppanel_lines;
> > +static char		*oppanel_data;
> > +static u32		line_length, num_lines;  
> 
> You calculate (num_lines * line_length) a lot, that would probably be
> worth storing as eg. "oppanel_size" or something.
> 
> > +
> > +static loff_t oppanel_llseek(struct file *filp, loff_t offset, int
> > whence) +{
> > +	return fixed_size_llseek(filp, offset, whence, num_lines *
> > +		line_length);  
> 
> I don't think you need to wrap that line?
> 
> > +}
> > +
> > +static ssize_t oppanel_read(struct file *filp, char __user
> > *userbuf, size_t len,
> > +		loff_t *f_pos)  
> 
> I prefer to align the second line unless the signature is
> ridiculously wide:
> 
> static ssize_t oppanel_read(struct file *filp, char __user *userbuf,
> size_t len, loff_t *f_pos)
I agree with all of the above and will fix.
> 
> > +{
> > +	return simple_read_from_buffer(userbuf, len, f_pos,
> > oppanel_data,
> > +		(num_lines * line_length));
> > +}
> > +
> > +static int __op_panel_write(void)  
> 
> Can you think of a better name for this?
__op_panel_update_display()?
> 
> > +{
> > +	int rc, token;
> > +	struct opal_msg msg;
> > +
> > +	token = opal_async_get_token_interruptible();
> > +	if (token < 0) {
> > +		if (token != -ERESTARTSYS)
> > +			pr_err("Couldn't get OPAL async token
> > [token=%d]\n",
> > +				token);
> > +		return token;
> > +	}
> > +
> > +	rc = opal_write_oppanel_async(token, oppanel_lines, (u64)
> > num_lines);  
> 
> I don't think you need the cast?
I don't think so either
> 
> > +	switch (rc) {
> > +	case OPAL_ASYNC_COMPLETION:
> > +		rc = opal_async_wait_response(token, &msg);
> > +		if (rc) {
> > +			pr_err("Failed to wait for async response
> > [rc=%d]\n",
> > +				rc);
> > +			goto out_token;
> > +		}
> > +		rc = be64_to_cpu(msg.params[1]);  
> 
> Is params[1] documented somewhere? Seems like a helper might be nice.
This is documented in skiboot in doc/opal-api/opal-messages.txt
I guess that would be a nice addition.
> 
> > +		if (rc != OPAL_SUCCESS) {
> > +			pr_err("OPAL async call returned failed
> > [rc=%d]\n", rc);
> > +			goto out_token;  
> 
> You don't need the goto do you? You can just break?
Yes
> 
> > +		}
> > +	case OPAL_SUCCESS:
> > +		break;
> > +	default:
> > +		pr_err("OPAL write op-panel call failed
> > [rc=%d]\n", rc);  
> 
> This and the other pr_err()s should be ratelimited, or become
> pr_debug().
pr_debug makes sense I think.
> 
> > +	}
> > +
> > +out_token:
> > +	opal_async_release_token(token);
> > +	return rc;
> > +}
> > +
> > +static ssize_t oppanel_write(struct file *filp, const char __user
> > *userbuf,
> > +		size_t len, loff_t *f_pos)
> > +{
> > +	ssize_t ret;
> > +	loff_t f_pos_prev = *f_pos;
> > +	int rc;
> > +
> > +	if (*f_pos >= (num_lines * line_length))
> > +		return -EFBIG;
> > +
> > +	ret = simple_write_to_buffer(oppanel_data, (num_lines *
> > +			line_length), f_pos, userbuf, len);  
> 
> AFAICS you never clear the buffer, so if I write "foobar" and then
> call write again with "foo", I'll end up with "foobar" on the panel?
> 
> Should you clear the buffer when the first write comes in (f_pos ==
> 0) ?
This was an implementation decision, but I agree now that it makes more
sense to clear the panel when writing at the start as it may not have
been you who wrote to it initially.
> 
> > +	if (ret > 0) {
> > +		rc = __op_panel_write();
> > +		if (rc != OPAL_SUCCESS) {
> > +			pr_err("OPAL call failed to write to op
> > panel display [rc=%d]\n",
> > +				rc);
> > +			*f_pos = f_pos_prev;
> > +			return -EIO;
> > +		}
> > +	}
> > +	return ret;
> > +}
> > +
> > +static int oppanel_open(struct inode *inode, struct file *filp)
> > +{
> > +	if (!mutex_trylock(&oppanel_mutex)) {
> > +		pr_debug("Device Busy\n");
> > +		return -EBUSY;
> > +	}
> > +	return 0;
> > +}
> > +
> > +static int oppanel_release(struct inode *inode, struct file *filp)
> > +{
> > +	mutex_unlock(&oppanel_mutex);
> > +	return 0;
> > +}
> > +
> > +static const struct file_operations oppanel_fops = {
> > +	.owner		= THIS_MODULE,
> > +	.llseek		= oppanel_llseek,
> > +	.read		= oppanel_read,
> > +	.write		= oppanel_write,
> > +	.open		= oppanel_open,
> > +	.release	= oppanel_release
> > +};
> > +
> > +static struct miscdevice oppanel_dev = {
> > +	.minor		= MISC_DYNAMIC_MINOR,
> > +	.name		= "oppanel",
> > +	.fops		= &oppanel_fops
> > +};
> > +
> > +static int oppanel_probe(struct platform_device *pdev)
> > +{
> > +	int rc, i;
> > +	struct device_node *dev_node = pdev->dev.of_node;  
> 
> dev_node should be called np.
> 
> > +	const u32 *length_val, *lines_val;  
> 
> My preference is reverse Christmas tree style:
> 
> 	const u32 *length_val, *lines_val;
> 	struct device_node *np;
> 	int rc, i;
> 
> 	np = pdev->dev.of_node;
> 
> > +
> > +	if (strncmp(dev_node->name, "oppanel", 7)) {  
> 
> You are using a compatible check (via the match table) so you don't
> need that check. Only checking the start of the name (7) would also
> be wrong.
> 
> > +		pr_err("Operator panel not found\n");
> > +		return -1;
> > +	}
> > +
> > +	length_val = of_get_property(dev_node, "#length", NULL);
> > +	if (!length_val) {
> > +		pr_err("Operator panel length property not
> > found\n");
> > +		return -1;
> > +	}
> > +	line_length = be32_to_cpu(*length_val);  
> 
> Please use of_property_read_u32(), you shouldn't need any endian
> conversions in this code.
> 
> > +	lines_val = of_get_property(dev_node, "#lines", NULL);
> > +	if (!lines_val) {
> > +		pr_err("Operator panel lines property not
> > found\n");
> > +		return -1;
> > +	}
> > +	num_lines = be32_to_cpu(*lines_val);  
> 
> Ditto.
> 
> > +	pr_debug("Operator panel found with %u lines of length
> > %u\n",
> > +			num_lines, line_length);  
> 
> pr_devel() would probably be even better (compiled out entirely).
> 
> > +	oppanel_data = kcalloc((num_lines * line_length),
> > sizeof(char),
> > +		GFP_KERNEL);
> > +	if (!oppanel_data)
> > +		return -ENOMEM;
> > +
> > +	oppanel_lines = kcalloc(num_lines, sizeof(oppanel_line_t),
> > GFP_KERNEL);
> > +	if (!oppanel_lines) {
> > +		kfree(oppanel_data);
> > +		return -ENOMEM;  
> 
> That should be:
> 		rc = -ENOMEM;
> 		goto free_oppanel;
> 
> > +	}
> > +
> > +	memset(oppanel_data, ' ', (num_lines * line_length));
> > +	for (i = 0; i < num_lines; i++) {
> > +		oppanel_lines[i].line_len = cpu_to_be64((u64)
> > line_length);
> > +		oppanel_lines[i].line = cpu_to_be64((u64)
> > &oppanel_data[i *
> > +						line_length]);  
> 
> We should be giving OPAL the real address of &oppanel_data[i *
> line_length], which means you need to wrap it in __pa(). Unless
> that's happening somewhere else I missed?
> 
> > +	}
> > +
> > +	mutex_init(&oppanel_mutex);  
> 
> AFAIK you don't need to do that because you used DEFINE_MUTEX() above?
> 
> > +	rc = misc_register(&oppanel_dev);
> > +	if (rc) {
> > +		pr_err("Failed to register as misc device\n");
> > +		goto remove_mutex;
> > +	}
> > +
> > +	pr_info("Device Successfully Initialised\n");  
> 
> We don't need a pr_info() on success.
> 
> > +	return 0;
> > +
> > +remove_mutex:
> > +	mutex_destroy(&oppanel_mutex);
> > +	kfree(oppanel_lines);
> > +	kfree(oppanel_data);
> > +	return rc;
> > +}
> > +
> > +static int oppanel_remove(struct platform_device *pdev)
> > +{
> > +	misc_deregister(&oppanel_dev);
> > +	mutex_destroy(&oppanel_mutex);
> > +	kfree(oppanel_lines);
> > +	kfree(oppanel_data);
> > +	pr_info("Device Successfully Removed\n");  
> 
> Don't need the pr_info().
> 
> cheers
I agree with all of the above and will fix up.
Thanks