Re: [PATCH v6 1/4] Runtime Interpreted Power Sequences

On 09/12/2012 03:57 AM, Alexandre Courbot wrote:

Some device drivers (panel backlights especially) need to follow precise
sequences for powering on and off, involving gpios, regulators, PWMs
with a precise powering order and delays to respect between each steps.
These sequences are board-specific, and do not belong to a particular
driver - therefore they have been performed by board-specific hook
functions to far.

With the advent of the device tree and of ARM kernels that are not
board-tied, we cannot rely on these board-specific hooks anymore but
need a way to implement these sequences in a portable manner. This patch
introduces a simple interpreter that can execute such power sequences
encoded either as platform data or within the device tree.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

+Sometimes, you may want to browse the list of resources allocated by a sequence,
+for instance to ensure that a resource of a given type is present. The
+power_seq_set_resources() function returns a list head that can be used with
+the power_seq_for_each_resource() macro to browse all the resources of a set:
+
+  struct list_head *power_seq_set_resources(struct power_seq_set *seqs);

I don't think you need to include that prototype here?

+  power_seq_for_each_resource(pos, seqs)
+
+Here "pos" will be a pointer to a struct power_seq_resource. This structure
+contains the type of the resource, the information used for identifying it, and
+the resolved resource itself.

Don't you need to compile all the power_seq_*.c too?

Oh, I see the following in power_seq.c:

+#include "power_seq_delay.c"
+#include "power_seq_regulator.c"
+#include "power_seq_pwm.c"
+#include "power_seq_gpio.c"

It's probably better just to compile them separately and link them.

+struct power_seq_step {
+	/* Copy of the platform data */
+	struct platform_power_seq_step pdata;

I'd reword the comment to "Copy of the step", and name the field "step".

+static const struct power_seq_res_ops power_seq_types[POWER_SEQ_NUM_TYPES] = {
+	[POWER_SEQ_DELAY] = POWER_SEQ_DELAY_TYPE,
+	[POWER_SEQ_REGULATOR] = POWER_SEQ_REGULATOR_TYPE,
+	[POWER_SEQ_PWM] = POWER_SEQ_PWM_TYPE,
+	[POWER_SEQ_GPIO] = POWER_SEQ_GPIO_TYPE,
+};

Ah, I see why you're using #include now.

+MODULE_LICENSE("GPL");

s/GPL/GPL v2/ given the license header.

+static int power_seq_res_alloc_gpio(struct device *dev,
+				    struct platform_power_seq_step *pstep,
+				    struct power_seq_resource *res)
+{
+	int err;
+
+	err = devm_gpio_request_one(dev, pstep->gpio.gpio,
+				    GPIOF_OUT_INIT_LOW, dev_name(dev));

Hmm. The INIT_LOW part of that might be somewhat presumptive. I would
suggest simply requesting the GPIO here, and using
gpio_direction_output() in power_seq_step_run_gpio(), thus deferring the
decision of what value to set the GPIO to until a real sequence is
actually run.

+#include <net/irda/parameters.h>

That looks out of place.

+/**
+ * struct power_seq_resource - resource used by a power sequence set
+ * @pdata:	Pointer to the platform data used to resolve this resource
+ * @regulator:	Resolved regulator if of type POWER_SEQ_REGULATOR
+ * @pwm:	Resolved PWM if of type POWER_SEQ_PWM
+ * @list:	Used to link resources together
+ */

I think that kerneldoc is stale.

+struct power_seq_resource {
+	enum power_seq_res_type type;
+	/* resolved resource and identifier */
+	union {
+		struct {
+			struct regulator *regulator;
+			const char *id;
+		} regulator;
+		struct {
+			struct pwm_device *pwm;
+			const char *id;
+		} pwm;
+		struct {
+			int gpio;
+		} gpio;
+	};
+	struct list_head list;
+};

Aside from those minor issues, this all looks reasonable to me, so,
Reviewed-by: Stephen Warren <redacted>