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Message-ID: <Ye07t/O8oOQRILyZ@kroah.com>
Date: Sun, 23 Jan 2022 12:27:51 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Sean Anderson <sean.anderson@...o.com>
Cc: linux-usb@...r.kernel.org,
Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: ulpi: Add debugfs support
On Fri, Jan 14, 2022 at 11:39:47AM -0500, Sean Anderson wrote:
> This adds a debugfs file for ULPI devices which contains a dump of their
> registers. This is useful for debugging basic connectivity problems. The
> file is created in ulpi_register because many devices will never have a
> driver bound (as they are managed in hardware by the USB controller
> device).
>
> Signed-off-by: Sean Anderson <sean.anderson@...o.com>
> ---
>
> drivers/usb/common/ulpi.c | 100 ++++++++++++++++++++++++++++++++++--
> include/linux/ulpi/driver.h | 3 ++
> 2 files changed, 99 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
> index 4169cf40a03b..a39c48e04013 100644
> --- a/drivers/usb/common/ulpi.c
> +++ b/drivers/usb/common/ulpi.c
> @@ -13,6 +13,7 @@
> #include <linux/module.h>
> #include <linux/slab.h>
> #include <linux/acpi.h>
> +#include <linux/debugfs.h>
> #include <linux/of.h>
> #include <linux/of_device.h>
> #include <linux/clk/clk-conf.h>
> @@ -228,9 +229,64 @@ static int ulpi_read_id(struct ulpi *ulpi)
> return 0;
> }
>
> +static int __maybe_unused ulpi_regs_read(struct seq_file *seq, void *data)
> +{
> + struct ulpi *ulpi = seq->private;
> +
> +#define ulpi_print(name, reg) do { \
> + int ret = ulpi_read(ulpi, reg); \
> + if (ret < 0) \
> + return ret; \
> + seq_printf(seq, name " %.02x\n", ret); \
> +} while (0)
> +
> + ulpi_print("Vendor ID Low ", ULPI_VENDOR_ID_LOW);
> + ulpi_print("Vendor ID High ", ULPI_VENDOR_ID_HIGH);
> + ulpi_print("Product ID Low ", ULPI_PRODUCT_ID_LOW);
> + ulpi_print("Product ID High ", ULPI_PRODUCT_ID_HIGH);
> + ulpi_print("Function Control ", ULPI_FUNC_CTRL);
> + ulpi_print("Interface Control ", ULPI_IFC_CTRL);
> + ulpi_print("OTG Control ", ULPI_OTG_CTRL);
> + ulpi_print("USB Interrupt Enable Rising ", ULPI_USB_INT_EN_RISE);
> + ulpi_print("USB Interrupt Enable Falling", ULPI_USB_INT_EN_FALL);
> + ulpi_print("USB Interrupt Status ", ULPI_USB_INT_STS);
> + ulpi_print("USB Interrupt Latch ", ULPI_USB_INT_LATCH);
> + ulpi_print("Debug ", ULPI_DEBUG);
> + ulpi_print("Scratch Register ", ULPI_SCRATCH);
> + ulpi_print("Carkit Control ", ULPI_CARKIT_CTRL);
> + ulpi_print("Carkit Interrupt Delay ", ULPI_CARKIT_INT_DELAY);
> + ulpi_print("Carkit Interrupt Enable ", ULPI_CARKIT_INT_EN);
> + ulpi_print("Carkit Interrupt Status ", ULPI_CARKIT_INT_STS);
> + ulpi_print("Carkit Interrupt Latch ", ULPI_CARKIT_INT_LATCH);
> + ulpi_print("Carkit Pulse Control ", ULPI_CARKIT_PLS_CTRL);
> + ulpi_print("Transmit Positive Width ", ULPI_TX_POS_WIDTH);
> + ulpi_print("Transmit Negative Width ", ULPI_TX_NEG_WIDTH);
> + ulpi_print("Receive Polarity Recovery ", ULPI_POLARITY_RECOVERY);
> +
> + return 0;
> +}
> +
> +static int __maybe_unused ulpi_regs_open(struct inode *inode, struct file *f)
> +{
> + struct ulpi *ulpi = inode->i_private;
> +
> + return single_open(f, ulpi_regs_read, ulpi);
> +}
> +
> +static const struct file_operations __maybe_unused ulpi_regs_ops = {
> + .owner = THIS_MODULE,
> + .open = ulpi_regs_open,
> + .release = single_release,
> + .read = seq_read,
> + .llseek = seq_lseek
> +};
> +
> +static struct dentry *ulpi_root = (void *)-EPROBE_DEFER;
There is no need for this variable, nor is there ever a need to set this
to an error value like this. If you need to find the root, just look it
up!
> +
> static int ulpi_register(struct device *dev, struct ulpi *ulpi)
> {
> int ret;
> + struct dentry *regs;
>
> ulpi->dev.parent = dev; /* needed early for ops */
> ulpi->dev.bus = &ulpi_bus;
> @@ -245,16 +301,39 @@ static int ulpi_register(struct device *dev, struct ulpi *ulpi)
>
> ret = ulpi_read_id(ulpi);
> if (ret)
> - return ret;
> + goto err_of;
>
> ret = device_register(&ulpi->dev);
> if (ret)
> - return ret;
> + goto err_of;
> +
> + if (IS_ENABLED(CONFIG_DEBUG_FS)) {
This check is not needed, the compiler will handle it all for your
automatically.
> + ulpi->root = debugfs_create_dir(dev_name(dev), ulpi_root);
> + if (IS_ERR(ulpi->root)) {
No need to check this, just keep moving on. debugfs return values
shoudl NEVER be checked as your code should not care what happens.
> + ret = PTR_ERR(ulpi->root);
> + goto err_dev;
> + }
> +
> + regs = debugfs_create_file("regs", 0444, ulpi->root, ulpi,
> + &ulpi_regs_ops);
Also, there is no need to save the dentry of "root", just make that a
local variable and look it up when you want to remove it.
> + if (IS_ERR(regs)) {
Again, no need to check this at all.
> + ret = PTR_ERR(regs);
> + goto err_debugfs;
> + }
> + }
All of this logic here can be reduced to 2 lines of code and one
variable:
struct dentry *dir;
...
dir = debugfs_create_dir(dev_name(dev),
debugfs_lookup(KBUILD_MODULE_NAME, NULL));
debugfs_create_file("regs", 0444, dir, ulpi, &ulpi_regs_ops);
and that's it.
>
> dev_dbg(&ulpi->dev, "registered ULPI PHY: vendor %04x, product %04x\n",
> ulpi->id.vendor, ulpi->id.product);
>
> return 0;
> +
> +err_debugfs:
> + debugfs_remove(ulpi->root);
debugfs_remove_recursive()?
> +err_dev:
> + device_unregister(&ulpi->dev);
> +err_of:
> + of_node_put(ulpi->dev.of_node);
> + return ret;
> }
>
> /**
> @@ -296,8 +375,9 @@ EXPORT_SYMBOL_GPL(ulpi_register_interface);
> */
> void ulpi_unregister_interface(struct ulpi *ulpi)
> {
> - of_node_put(ulpi->dev.of_node);
> + debugfs_remove_recursive(ulpi->root);
again, look up the name you want to remove, no need to store it around
anywhere:
debugfs_remove_recursive(debugfs_lookup(dev_name(ulpi->dev), debugfs_lookup(KBUILD_MODULE_NAME, NULL)));
> device_unregister(&ulpi->dev);
> + of_node_put(ulpi->dev.of_node);
> }
> EXPORT_SYMBOL_GPL(ulpi_unregister_interface);
>
> @@ -305,13 +385,25 @@ EXPORT_SYMBOL_GPL(ulpi_unregister_interface);
>
> static int __init ulpi_init(void)
> {
> - return bus_register(&ulpi_bus);
> + int ret;
> +
> + if (IS_ENABLED(CONFIG_DEBUG_FS)) {
Again, no need to check
> + ulpi_root = debugfs_create_dir("ulpi", NULL);
Again, no need to keep this, it can just be:
debugfs_create_dir(KBUILD_MODULE_NAME, NULL);
> + if (IS_ERR(ulpi_root))
> + return PTR_ERR(ulpi_root);
> + }
> +
> + ret = bus_register(&ulpi_bus);
> + if (ret)
> + debugfs_remove(ulpi_root);
> + return ret;
> }
> subsys_initcall(ulpi_init);
>
> static void __exit ulpi_exit(void)
> {
> bus_unregister(&ulpi_bus);
> + debugfs_remove(ulpi_root);
debugfs_remove_recursive(debugfs_lookup(KBUILD_MODULE_NAME, NULL));
> }
> module_exit(ulpi_exit);
>
> diff --git a/include/linux/ulpi/driver.h b/include/linux/ulpi/driver.h
> index c7a1810373e3..083ea2d2e873 100644
> --- a/include/linux/ulpi/driver.h
> +++ b/include/linux/ulpi/driver.h
> @@ -6,6 +6,7 @@
>
> #include <linux/device.h>
>
> +struct dentry;
> struct ulpi_ops;
>
> /**
> @@ -13,10 +14,12 @@ struct ulpi_ops;
> * @id: vendor and product ids for ULPI device
> * @ops: I/O access
> * @dev: device interface
> + * @root: root directory for debugfs files
No need for this, as pointed out above.
This should make you patch a _lot_ smaller.
thanks,
greg k-h
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