Date:   Sun, 18 Aug 2019 20:38:36 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 1/2] irq/irq_sim: make the irq_sim structure opaque

On Mon, 12 Aug 2019 14:52:55 +0200
Bartosz Golaszewski <brgl@...ev.pl> wrote:

> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> There's no good reason to export the interrupt simulator structure to
> users and have them provide memory for it. Let's make all the related
> data structures opaque and convert both users. This way we have a lot
> less APIs exposed in the header.
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>

I agree in principle, but there is the disadvantage that all drivers
that use it now need to bother with another allocation.  I guess
it is still worthwhile though.

One comment inline.

Jonathan

> ---
>  drivers/gpio/gpio-mockup.c          | 12 ++---
>  drivers/iio/dummy/iio_dummy_evgen.c | 18 +++----
>  include/linux/irq_sim.h             | 24 ++-------
>  kernel/irq/irq_sim.c                | 83 ++++++++++++++++++-----------
>  4 files changed, 70 insertions(+), 67 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
> index f1a9c0544e3f..9b28ffec5826 100644
> --- a/drivers/gpio/gpio-mockup.c
> +++ b/drivers/gpio/gpio-mockup.c
> @@ -53,7 +53,7 @@ struct gpio_mockup_line_status {
>  struct gpio_mockup_chip {
>  	struct gpio_chip gc;
>  	struct gpio_mockup_line_status *lines;
> -	struct irq_sim irqsim;
> +	struct irq_sim *irqsim;
>  	struct dentry *dbg_dir;
>  	struct mutex lock;
>  };
> @@ -186,7 +186,7 @@ static int gpio_mockup_to_irq(struct gpio_chip *gc, unsigned int offset)
>  {
>  	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
>  
> -	return irq_sim_irqnum(&chip->irqsim, offset);
> +	return irq_sim_irqnum(chip->irqsim, offset);
>  }
>  
>  static void gpio_mockup_free(struct gpio_chip *gc, unsigned int offset)
> @@ -247,7 +247,7 @@ static ssize_t gpio_mockup_debugfs_write(struct file *file,
>  	chip = priv->chip;
>  	gc = &chip->gc;
>  	desc = &gc->gpiodev->descs[priv->offset];
> -	sim = &chip->irqsim;
> +	sim = chip->irqsim;
>  
>  	mutex_lock(&chip->lock);
>  
> @@ -431,9 +431,9 @@ static int gpio_mockup_probe(struct platform_device *pdev)
>  			return rv;
>  	}
>  
> -	rv = devm_irq_sim_init(dev, &chip->irqsim, gc->ngpio);
> -	if (rv < 0)
> -		return rv;
> +	chip->irqsim = devm_irq_sim_new(dev, gc->ngpio);
> +	if (IS_ERR(chip->irqsim))
> +		return PTR_ERR(chip->irqsim);
>  
>  	rv = devm_gpiochip_add_data(dev, &chip->gc, chip);
>  	if (rv)
> diff --git a/drivers/iio/dummy/iio_dummy_evgen.c b/drivers/iio/dummy/iio_dummy_evgen.c
> index a6edf30567aa..efbcd4a5609e 100644
> --- a/drivers/iio/dummy/iio_dummy_evgen.c
> +++ b/drivers/iio/dummy/iio_dummy_evgen.c
> @@ -37,7 +37,7 @@ struct iio_dummy_eventgen {
>  	struct iio_dummy_regs regs[IIO_EVENTGEN_NO];
>  	struct mutex lock;
>  	bool inuse[IIO_EVENTGEN_NO];
> -	struct irq_sim irq_sim;
> +	struct irq_sim *irq_sim;
>  	int base;
>  };
>  
> @@ -46,19 +46,17 @@ static struct iio_dummy_eventgen *iio_evgen;
>  
>  static int iio_dummy_evgen_create(void)
>  {
> -	int ret;
> -
>  	iio_evgen = kzalloc(sizeof(*iio_evgen), GFP_KERNEL);
>  	if (!iio_evgen)
>  		return -ENOMEM;
>  
> -	ret = irq_sim_init(&iio_evgen->irq_sim, IIO_EVENTGEN_NO);
> -	if (ret < 0) {
> +	iio_evgen->irq_sim = irq_sim_new(IIO_EVENTGEN_NO);
> +	if (IS_ERR(iio_evgen->irq_sim)) {
>  		kfree(iio_evgen);
> -		return ret;
> +		return PTR_ERR(iio_evgen->irq_sim);
>  	}
>  
> -	iio_evgen->base = irq_sim_irqnum(&iio_evgen->irq_sim, 0);
> +	iio_evgen->base = irq_sim_irqnum(iio_evgen->irq_sim, 0);
>  	mutex_init(&iio_evgen->lock);
>  
>  	return 0;
> @@ -80,7 +78,7 @@ int iio_dummy_evgen_get_irq(void)
>  	mutex_lock(&iio_evgen->lock);
>  	for (i = 0; i < IIO_EVENTGEN_NO; i++) {
>  		if (!iio_evgen->inuse[i]) {
> -			ret = irq_sim_irqnum(&iio_evgen->irq_sim, i);
> +			ret = irq_sim_irqnum(iio_evgen->irq_sim, i);
>  			iio_evgen->inuse[i] = true;
>  			break;
>  		}
> @@ -115,7 +113,7 @@ EXPORT_SYMBOL_GPL(iio_dummy_evgen_get_regs);
>  
>  static void iio_dummy_evgen_free(void)
>  {
> -	irq_sim_fini(&iio_evgen->irq_sim);
> +	irq_sim_free(iio_evgen->irq_sim);
>  	kfree(iio_evgen);
>  }
>  
> @@ -140,7 +138,7 @@ static ssize_t iio_evgen_poke(struct device *dev,
>  	iio_evgen->regs[this_attr->address].reg_id   = this_attr->address;
>  	iio_evgen->regs[this_attr->address].reg_data = event;
>  
> -	irq_sim_fire(&iio_evgen->irq_sim, this_attr->address);
> +	irq_sim_fire(iio_evgen->irq_sim, this_attr->address);
>  
>  	return len;
>  }
> diff --git a/include/linux/irq_sim.h b/include/linux/irq_sim.h
> index 4500d453a63e..4bbf036145e2 100644
> --- a/include/linux/irq_sim.h
> +++ b/include/linux/irq_sim.h
> @@ -14,27 +14,11 @@
>   * requested like normal irqs and enqueued from process context.
>   */
>  
> -struct irq_sim_work_ctx {
> -	struct irq_work		work;
> -	unsigned long		*pending;
> -};
> +struct irq_sim;
>  
> -struct irq_sim_irq_ctx {
> -	int			irqnum;
> -	bool			enabled;
> -};
> -
> -struct irq_sim {
> -	struct irq_sim_work_ctx	work_ctx;
> -	int			irq_base;
> -	unsigned int		irq_count;
> -	struct irq_sim_irq_ctx	*irqs;
> -};
> -
> -int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs);
> -int devm_irq_sim_init(struct device *dev, struct irq_sim *sim,
> -		      unsigned int num_irqs);
> -void irq_sim_fini(struct irq_sim *sim);
> +struct irq_sim *irq_sim_new(unsigned int num_irqs);
> +struct irq_sim *devm_irq_sim_new(struct device *dev, unsigned int num_irqs);
> +void irq_sim_free(struct irq_sim *sim);
>  void irq_sim_fire(struct irq_sim *sim, unsigned int offset);
>  int irq_sim_irqnum(struct irq_sim *sim, unsigned int offset);
>  
> diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c
> index b992f88c5613..79f0a6494b6c 100644
> --- a/kernel/irq/irq_sim.c
> +++ b/kernel/irq/irq_sim.c
> @@ -7,6 +7,23 @@
>  #include <linux/irq_sim.h>
>  #include <linux/irq.h>
>  
> +struct irq_sim_work_ctx {
> +	struct irq_work		work;
> +	unsigned long		*pending;
> +};
> +
> +struct irq_sim_irq_ctx {
> +	int			irqnum;
> +	bool			enabled;
> +};
> +
> +struct irq_sim {
> +	struct irq_sim_work_ctx	work_ctx;
> +	int			irq_base;
> +	unsigned int		irq_count;
> +	struct irq_sim_irq_ctx	*irqs;
> +};
> +
>  struct irq_sim_devres {
>  	struct irq_sim		*sim;
>  };
> @@ -63,34 +80,42 @@ static void irq_sim_handle_irq(struct irq_work *work)
>  }
>  
>  /**
> - * irq_sim_init - Initialize the interrupt simulator: allocate a range of
> - *                dummy interrupts.
> + * irq_sim_new - Create a new interrupt simulator: allocate a range of
> + *               dummy interrupts.
>   *
> - * @sim:        The interrupt simulator object to initialize.
>   * @num_irqs:   Number of interrupts to allocate
>   *
> - * On success: return the base of the allocated interrupt range.
> - * On failure: a negative errno.
> + * On success: return the new irq_sim object.
> + * On failure: a negative errno wrapped with ERR_PTR().
>   */
> -int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs)
> +struct irq_sim *irq_sim_new(unsigned int num_irqs)
>  {
> +	struct irq_sim *sim;
>  	int i;
>  
> +	sim = kmalloc(sizeof(*sim), GFP_KERNEL);
> +	if (!sim)
> +		return ERR_PTR(-ENOMEM);
> +
>  	sim->irqs = kmalloc_array(num_irqs, sizeof(*sim->irqs), GFP_KERNEL);
> -	if (!sim->irqs)
> -		return -ENOMEM;
> +	if (!sim->irqs) {
> +		kfree(sim);
> +		return ERR_PTR(-ENOMEM);
> +	}
>  
>  	sim->irq_base = irq_alloc_descs(-1, 0, num_irqs, 0);
>  	if (sim->irq_base < 0) {
>  		kfree(sim->irqs);
> -		return sim->irq_base;
> +		kfree(sim);
> +		return ERR_PTR(sim->irq_base);
>  	}
>  
>  	sim->work_ctx.pending = bitmap_zalloc(num_irqs, GFP_KERNEL);
>  	if (!sim->work_ctx.pending) {
>  		kfree(sim->irqs);
> +		kfree(sim);

This rather looks like a function that could benefit from some
unified error paths.  That was true already, but adding another step
makes it an even better idea. Goto fun :)

>  		irq_free_descs(sim->irq_base, num_irqs);
> -		return -ENOMEM;
> +		return ERR_PTR(-ENOMEM);
>  	}
>  
>  	for (i = 0; i < num_irqs; i++) {
> @@ -106,64 +131,60 @@ int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs)
>  	init_irq_work(&sim->work_ctx.work, irq_sim_handle_irq);
>  	sim->irq_count = num_irqs;
>  
> -	return sim->irq_base;
> +	return sim;
>  }
> -EXPORT_SYMBOL_GPL(irq_sim_init);
> +EXPORT_SYMBOL_GPL(irq_sim_new);
>  
>  /**
> - * irq_sim_fini - Deinitialize the interrupt simulator: free the interrupt
> + * irq_sim_free - Deinitialize the interrupt simulator: free the interrupt
>   *                descriptors and allocated memory.
>   *
>   * @sim:        The interrupt simulator to tear down.
>   */
> -void irq_sim_fini(struct irq_sim *sim)
> +void irq_sim_free(struct irq_sim *sim)
>  {
>  	irq_work_sync(&sim->work_ctx.work);
>  	bitmap_free(sim->work_ctx.pending);
>  	irq_free_descs(sim->irq_base, sim->irq_count);
>  	kfree(sim->irqs);
> +	kfree(sim);
>  }
> -EXPORT_SYMBOL_GPL(irq_sim_fini);
> +EXPORT_SYMBOL_GPL(irq_sim_free);
>  
>  static void devm_irq_sim_release(struct device *dev, void *res)
>  {
>  	struct irq_sim_devres *this = res;
>  
> -	irq_sim_fini(this->sim);
> +	irq_sim_free(this->sim);
>  }
>  
>  /**
> - * irq_sim_init - Initialize the interrupt simulator for a managed device.
> + * devm_irq_sim_new - Create a new interrupt simulator for a managed device.
>   *
>   * @dev:        Device to initialize the simulator object for.
> - * @sim:        The interrupt simulator object to initialize.
>   * @num_irqs:   Number of interrupts to allocate
>   *
> - * On success: return the base of the allocated interrupt range.
> - * On failure: a negative errno.
> + * On success: return a new irq_sim object.
> + * On failure: a negative errno wrapped with ERR_PTR().
>   */
> -int devm_irq_sim_init(struct device *dev, struct irq_sim *sim,
> -		      unsigned int num_irqs)
> +struct irq_sim *devm_irq_sim_new(struct device *dev, unsigned int num_irqs)
>  {
>  	struct irq_sim_devres *dr;
> -	int rv;
>  
>  	dr = devres_alloc(devm_irq_sim_release, sizeof(*dr), GFP_KERNEL);
>  	if (!dr)
> -		return -ENOMEM;
> +		return ERR_PTR(-ENOMEM);
>  
> -	rv = irq_sim_init(sim, num_irqs);
> -	if (rv < 0) {
> +	dr->sim = irq_sim_new(num_irqs);
> +	if (IS_ERR(dr->sim)) {
>  		devres_free(dr);
> -		return rv;
> +		return dr->sim;
>  	}
>  
> -	dr->sim = sim;
>  	devres_add(dev, dr);
> -
> -	return rv;
> +	return dr->sim;
>  }
> -EXPORT_SYMBOL_GPL(devm_irq_sim_init);
> +EXPORT_SYMBOL_GPL(devm_irq_sim_new);
>  
>  /**
>   * irq_sim_fire - Enqueue an interrupt.

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