Re: [PATCH v10 3/7] qcom-tgu: Add signal priority support

[Songwei Chai]

On 1/13/2026 7:09 PM, Konrad Dybcio wrote:
> On 1/9/26 3:11 AM, Songwei Chai wrote:
> > Like circuit of a Logic analyzer, in TGU, the requirement could be
> > configured in each step and the trigger will be created once the
> > requirements are met. Add priority functionality here to sort the
> > signals into different priorities. The signal which is wanted could
> > be configured in each step's priority node, the larger number means
> > the higher priority and the signal with higher priority will be sensed
> > more preferentially.
> >
> > Signed-off-by: Songwei Chai <songwei.chai@xxxxxxxxxxxxxxxx>
> > ---
>
> [...]
>
> > +static ssize_t tgu_dataset_store(struct device *dev,
> > +				 struct device_attribute *attr,
> > +				 const char *buf, size_t size)
> > +{
> > +	struct tgu_drvdata *tgu_drvdata = dev_get_drvdata(dev);
> > +	struct tgu_attribute *tgu_attr =
> > +		container_of(attr, struct tgu_attribute, attr);
> > +	unsigned long val;
> > +	int index;
> > +
> > +	ret = kstrtoul(buf, 0, &val);
> > +	if (ret)
> > +		return ret;
> > +
> > +	guard(spinlock)(&tgu_drvdata->lock);
> > +	index = calculate_array_location(tgu_drvdata, tgu_attr->step_index,
> > +					 tgu_attr->operation_index,
> > +					 tgu_attr->reg_num);
> > +
> > +	tgu_drvdata->value_table->priority[index] = val;
> > +	return size;
>
> Style: some functions have a \n before return, some don't. The former
> is preferred
Sure, Konrad.
I will update and pay more attention next time.
> > +static umode_t tgu_node_visible(struct kobject *kobject,
> > +				struct attribute *attr,
> > +				int n)
> > +{
> > +	struct device *dev = kobj_to_dev(kobject);
> > +	struct tgu_drvdata *drvdata = dev_get_drvdata(dev);
> > +	struct device_attribute *dev_attr =
> > +		container_of(attr, struct device_attribute, attr);
> > +	struct tgu_attribute *tgu_attr =
> > +		container_of(dev_attr, struct tgu_attribute, attr);
> > +	int ret = SYSFS_GROUP_INVISIBLE;
> > +
> > +	if (tgu_attr->step_index < drvdata->max_step) {
> > +		ret = (tgu_attr->reg_num < drvdata->max_reg) ?
> > +			attr->mode : 0;
> > +	}
> > +	return ret;
>
> This is very convoluted
>
> How about:
>
> if (tgu_attr->step_index >= drvdata->max_step)
> 	return 0;
>
> if (tgu_attr->reg_num >= drvdata->max_reg)
> 	return 0;
>
> return attr->mode;
>
> ?
>
> [...]
I agree that the expanded form is clearer step-by-step, but I 
intentionally kept the current version as it keeps the bounds checks 
localized and avoids multiple early returns in this simple case.

I find the conditional expression still reasonably readable here, but 
I’m happy to revisit this if you feel strongly about the style.
> > +static void tgu_set_reg_number(struct tgu_drvdata *drvdata)
> > +{
> > +	int num_sense_input;
> > +	int num_reg;
> > +	u32 devid;
> > +
> > +	devid = readl(drvdata->base + TGU_DEVID);
> > +
> > +	num_sense_input = TGU_DEVID_SENSE_INPUT(devid);
> > +	if (((num_sense_input * NUMBER_BITS_EACH_SIGNAL) % LENGTH_REGISTER) == 0)
> > +		num_reg = (num_sense_input * NUMBER_BITS_EACH_SIGNAL) / LENGTH_REGISTER;
> > +	else
> > +		num_reg = ((num_sense_input * NUMBER_BITS_EACH_SIGNAL) / LENGTH_REGISTER) + 1;
>
> num_reg = base case
>
> if (num_sense_input * NUMBER_BITS_EACH_SIGNAL) % LENGTH_REGISTER)
> 	num_reg++;
>
> ?
Marked, will update.
> [...]
>
> > @@ -112,6 +250,8 @@ static int tgu_probe(struct amba_device *adev, const struct amba_id *id)
> >   {
> >   	struct device *dev = &adev->dev;
> >   	struct tgu_drvdata *drvdata;
> > +	size_t priority_size;
> > +	unsigned int *priority;
>
> reverse-Christmas-tree would be nice
Marked, will update.
> >   	int ret;
> >   
> >   	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> > @@ -127,12 +267,32 @@ static int tgu_probe(struct amba_device *adev, const struct amba_id *id)
> >   
> >   	spin_lock_init(&drvdata->lock);
> >   
> > +	tgu_set_reg_number(drvdata);
> > +	tgu_set_steps(drvdata);
> > +
> >   	ret = sysfs_create_groups(&dev->kobj, tgu_attr_groups);
> >   	if (ret) {
> >   		dev_err(dev, "failed to create sysfs groups: %d\n", ret);
> >   		return ret;
> >   	}
> >   
> > +	drvdata->value_table =
> > +		devm_kzalloc(dev, sizeof(*drvdata->value_table), GFP_KERNEL);
> > +	if (!drvdata->value_table)
> > +		return -ENOMEM;
> > +
> > +	priority_size = MAX_PRIORITY * drvdata->max_reg *
> > +			drvdata->max_step *
> > +			sizeof(*(drvdata->value_table->priority));
> > +
> > +	priority = devm_kzalloc(dev, priority_size, GFP_KERNEL);
> > +
> > +	if (!priority)
>
> stray \n above
Marked, will update.
> [...]
>
> > +#define BMVAL(val, lsb, msb)	((val & GENMASK(msb, lsb)) >> lsb)
> > +#define TGU_DEVID_SENSE_INPUT(devid_val) ((int) BMVAL(devid_val, 10, 17))
> > +#define TGU_DEVID_STEPS(devid_val) ((int)BMVAL(devid_val, 3, 6))
> > +#define NUMBER_BITS_EACH_SIGNAL 4
>
> "TGU_BITS_PER_SIGNAL"
Marked, will update.
> Konrad