| Message ID | 20240326141108.1079993-2-ckeepax@opensource.cirrus.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Add bridged amplifiers to cs42l43 | expand |
On Tue, Mar 26, 2024 at 3:11 PM Charles Keepax <ckeepax@opensource.cirrus.com> wrote: > SPI devices can specify a cs-gpios property to enumerate their > chip selects. Under device tree, a zero entry in this property can > be used to specify that a particular chip select is using the SPI > controllers native chip select, for example: > > cs-gpios = <&gpio1 0 0>, <0>; > > Here the second chip select is native. However, when using swnodes > there is currently no way to specify a native chip select. The > proposal here is to register a swnode_gpio_undefined software node, > that can be specified to allow the indication of a native chip > select. For example: > > static const struct software_node_ref_args device_cs_refs[] = { > { > .node = &device_gpiochip_swnode, > .nargs = 2, > .args = { 0, GPIO_ACTIVE_LOW }, > }, > { > .node = &swnode_gpio_undefined, > .nargs = 0, > }, > }; > > Register the swnode as the gpiolib is initialised and > check in swnode_get_gpio_device if the returned node matches > swnode_gpio_undefined and return -ENOENT, which matches the behaviour > of the device tree system when it encounters a 0 phandle. > > Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com> Hm that's an interesting corner case. > +const struct software_node swnode_gpio_undefined = { > + .name = "gpio-internal-undefined", > +}; > +EXPORT_SYMBOL_GPL(swnode_gpio_undefined); This needs a comment in the code telling exactly why this is here. It is also taking up space and code here on systems that have no use for it, so I wonder if it is possible to make this optional. > + if (!strcmp(gdev_node->name, "gpio-internal-undefined")) > + return ERR_PTR(-ENOENT); This needs a comment stating why this check is here, it's not obvious. Yours, Linus Walleij
On Tue, Mar 26, 2024 at 02:11:06PM +0000, Charles Keepax wrote: > SPI devices can specify a cs-gpios property to enumerate their > chip selects. Under device tree, a zero entry in this property can > be used to specify that a particular chip select is using the SPI > controllers native chip select, for example: > > cs-gpios = <&gpio1 0 0>, <0>; > > Here the second chip select is native. However, when using swnodes > there is currently no way to specify a native chip select. The > proposal here is to register a swnode_gpio_undefined software node, > that can be specified to allow the indication of a native chip > select. For example: > > static const struct software_node_ref_args device_cs_refs[] = { > { > .node = &device_gpiochip_swnode, > .nargs = 2, > .args = { 0, GPIO_ACTIVE_LOW }, > }, > { > .node = &swnode_gpio_undefined, > .nargs = 0, > }, > }; I am sorry, I am very late to the party, but wouldn't it all work by simply setting ".node" to NULL? As far as I can see we have in software_node_get_reference_args(): ... if (index * sizeof(*ref) >= prop->length) return -ENOENT; ref_array = prop->pointer; ref = &ref_array[index]; refnode = software_node_fwnode(ref->node); if (!refnode) return -ENOENT; if ref->node is NULL then software_node_fwnode(ref->node) will return NULL and we'll get -ENOENT which will bubble up to gpiod_get_index_optional() in SPI core. Thanks.
On Tue, Dec 10, 2024 at 04:15:18PM -0800, Dmitry Torokhov wrote: > On Tue, Mar 26, 2024 at 02:11:06PM +0000, Charles Keepax wrote: > > SPI devices can specify a cs-gpios property to enumerate their > > chip selects. Under device tree, a zero entry in this property can > > be used to specify that a particular chip select is using the SPI > > controllers native chip select, for example: > > > > cs-gpios = <&gpio1 0 0>, <0>; > > > > Here the second chip select is native. However, when using swnodes > > there is currently no way to specify a native chip select. The > > proposal here is to register a swnode_gpio_undefined software node, > > that can be specified to allow the indication of a native chip > > select. For example: > > > > static const struct software_node_ref_args device_cs_refs[] = { > > { > > .node = &device_gpiochip_swnode, > > .nargs = 2, > > .args = { 0, GPIO_ACTIVE_LOW }, > > }, > > { > > .node = &swnode_gpio_undefined, > > .nargs = 0, > > }, > > }; > > I am sorry, I am very late to the party, but wouldn't it all work by > simply setting ".node" to NULL? As far as I can see we have in > software_node_get_reference_args(): > > ... > > if (index * sizeof(*ref) >= prop->length) > return -ENOENT; > > ref_array = prop->pointer; > ref = &ref_array[index]; > > refnode = software_node_fwnode(ref->node); > if (!refnode) > return -ENOENT; > > if ref->node is NULL then software_node_fwnode(ref->node) will return > NULL and we'll get -ENOENT which will bubble up to > gpiod_get_index_optional() in SPI core. > I did definitely try that at the time, and there was definitely some issue with that approach. I think it might have related to something around how the GPIO stuff structures things. Alas, it is long enough ago that the details are escaping me, if I manage to find a spare minute I will try to refresh my memory and report back. Thanks, Charles
diff --git a/drivers/gpio/gpiolib-swnode.c b/drivers/gpio/gpiolib-swnode.c index fa52bdb1a29a..801b5a660307 100644 --- a/drivers/gpio/gpiolib-swnode.c +++ b/drivers/gpio/gpiolib-swnode.c @@ -17,6 +17,11 @@ #include "gpiolib.h" #include "gpiolib-swnode.h" +const struct software_node swnode_gpio_undefined = { + .name = "gpio-internal-undefined", +}; +EXPORT_SYMBOL_GPL(swnode_gpio_undefined); + static void swnode_format_propname(const char *con_id, char *propname, size_t max_size) { @@ -40,6 +45,9 @@ static struct gpio_device *swnode_get_gpio_device(struct fwnode_handle *fwnode) if (!gdev_node || !gdev_node->name) return ERR_PTR(-EINVAL); + if (!strcmp(gdev_node->name, "gpio-internal-undefined")) + return ERR_PTR(-ENOENT); + gdev = gpio_device_find_by_label(gdev_node->name); return gdev ?: ERR_PTR(-EPROBE_DEFER); } diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index ce94e37bcbee..e3a7e2a3a323 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -4892,8 +4892,17 @@ DEFINE_SEQ_ATTRIBUTE(gpiolib); static int __init gpiolib_debugfs_init(void) { + int ret; + + ret = software_node_register(&swnode_gpio_undefined); + if (ret < 0) { + pr_err("gpiolib: failed to register swnode: %d\n", ret); + return ret; + } + /* /sys/kernel/debug/gpio */ debugfs_create_file("gpio", 0444, NULL, NULL, &gpiolib_fops); + return 0; } subsys_initcall(gpiolib_debugfs_init); diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h index db2dfbae8edb..e685fac43398 100644 --- a/include/linux/gpio/consumer.h +++ b/include/linux/gpio/consumer.h @@ -12,6 +12,8 @@ struct fwnode_handle; struct gpio_array; struct gpio_desc; +struct software_node; + /** * struct gpio_descs - Struct containing an array of descriptors that can be * obtained using gpiod_get_array() @@ -54,6 +56,8 @@ enum gpiod_flags { GPIOD_OUT_HIGH_OPEN_DRAIN = GPIOD_OUT_HIGH | GPIOD_FLAGS_BIT_OPEN_DRAIN, }; +extern const struct software_node swnode_gpio_undefined; + #ifdef CONFIG_GPIOLIB /* Return the number of GPIOs associated with a device / function */
SPI devices can specify a cs-gpios property to enumerate their chip selects. Under device tree, a zero entry in this property can be used to specify that a particular chip select is using the SPI controllers native chip select, for example: cs-gpios = <&gpio1 0 0>, <0>; Here the second chip select is native. However, when using swnodes there is currently no way to specify a native chip select. The proposal here is to register a swnode_gpio_undefined software node, that can be specified to allow the indication of a native chip select. For example: static const struct software_node_ref_args device_cs_refs[] = { { .node = &device_gpiochip_swnode, .nargs = 2, .args = { 0, GPIO_ACTIVE_LOW }, }, { .node = &swnode_gpio_undefined, .nargs = 0, }, }; Register the swnode as the gpiolib is initialised and check in swnode_get_gpio_device if the returned node matches swnode_gpio_undefined and return -ENOENT, which matches the behaviour of the device tree system when it encounters a 0 phandle. Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com> --- drivers/gpio/gpiolib-swnode.c | 8 ++++++++ drivers/gpio/gpiolib.c | 9 +++++++++ include/linux/gpio/consumer.h | 4 ++++ 3 files changed, 21 insertions(+)