Date:   Wed, 13 May 2020 17:57:39 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     Moritz Fischer <mdf@...nel.org>
Cc:     linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org,
        trix@...hat.com, bhu@...hat.com, Luwei Kang <luwei.kang@...el.com>,
        Wu Hao <hao.wu@...el.com>
Subject: Re: [PATCH v5 3/7] fpga: dfl: introduce interrupt trigger setting API

On Mon, May 11, 2020 at 09:16:34PM -0700, Moritz Fischer wrote:
> On Mon, Apr 20, 2020 at 04:11:39PM +0800, Xu Yilun wrote:
> > FPGA user applications may be interested in interrupts generated by
> > DFL features. For example, users can implement their own FPGA
> > logics with interrupts enabled in AFU (Accelerated Function Unit,
> > dynamic region of DFL based FPGA). So user applications need to be
> > notified to handle these interrupts.
> > 
> > In order to allow userspace applications to monitor interrupts,
> > driver requires userspace to provide eventfds as interrupt
> > notification channels. Applications then poll/select on the eventfds
> > to get notified.
> > 
> > This patch introduces a generic helper functions to do eventfds binding
> > with given interrupts.
> > 
> > Sub feature drivers are expected to use XXX_GET_IRQ_NUM to query irq
> > info, and XXX_SET_IRQ to set eventfds for interrupts. This patch also
> > introduces helper functions for these 2 ioctls.
> > 
> > Signed-off-by: Luwei Kang <luwei.kang@...el.com>
> > Signed-off-by: Wu Hao <hao.wu@...el.com>
> > Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> > Acked-by: Wu Hao <hao.wu@...el.com>
> > ----
> > v2: use unsigned int instead of int for irq array indexes in
> >     dfl_fpga_set_irq_triggers()
> >     Improves comments for NULL fds param in dfl_fpga_set_irq_triggers()
> > v3: Improve comments of dfl_fpga_set_irq_triggers()
> >     refines code for dfl_fpga_set_irq_triggers, delete local variable j
> > v4: Introduce 2 helper functions to help handle the XXX_GET_IRQ_NUM &
> >     XXX_SET_IRQ ioctls for sub feature drivers.
> > v5: Some minor fix for Hao's comments
> > ---
> >  drivers/fpga/dfl.c            | 156 ++++++++++++++++++++++++++++++++++++++++++
> >  drivers/fpga/dfl.h            |  17 +++++
> >  include/uapi/linux/fpga-dfl.h |  13 ++++
> >  3 files changed, 186 insertions(+)
> > 
> > diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
> > index b49fbed..208d8f0 100644
> > --- a/drivers/fpga/dfl.c
> > +++ b/drivers/fpga/dfl.c
> > @@ -10,7 +10,9 @@
> >   *   Wu Hao <hao.wu@...el.com>
> >   *   Xiao Guangrong <guangrong.xiao@...ux.intel.com>
> >   */
> > +#include <linux/fpga-dfl.h>
> >  #include <linux/module.h>
> > +#include <linux/uaccess.h>
> >  
> >  #include "dfl.h"
> >  
> > @@ -534,6 +536,7 @@ static int build_info_commit_dev(struct build_feature_devs_info *binfo)
> >  		unsigned int i;
> >  
> >  		/* save resource information for each feature */
> > +		feature->dev = fdev;
> >  		feature->id = finfo->fid;
> >  		feature->resource_index = index;
> >  		feature->ioaddr = finfo->ioaddr;
> > @@ -1395,6 +1398,159 @@ int dfl_fpga_cdev_config_ports_vf(struct dfl_fpga_cdev *cdev, int num_vfs)
> >  }
> >  EXPORT_SYMBOL_GPL(dfl_fpga_cdev_config_ports_vf);
> >  
> > +static irqreturn_t dfl_irq_handler(int irq, void *arg)
> > +{
> > +	struct eventfd_ctx *trigger = arg;
> > +
> > +	eventfd_signal(trigger, 1);
> > +	return IRQ_HANDLED;
> > +}
> > +
> > +static int do_set_irq_trigger(struct dfl_feature *feature, unsigned int idx,
> > +			      int fd)
> > +{
> > +	struct platform_device *pdev = feature->dev;
> > +	struct eventfd_ctx *trigger;
> > +	int irq, ret;
> > +
> > +	if (idx >= feature->nr_irqs)
> > +		return -EINVAL;
> > +
> > +	irq = feature->irq_ctx[idx].irq;
> > +
> > +	if (feature->irq_ctx[idx].trigger) {
> > +		free_irq(irq, feature->irq_ctx[idx].trigger);
> > +		kfree(feature->irq_ctx[idx].name);
> > +		eventfd_ctx_put(feature->irq_ctx[idx].trigger);
> > +		feature->irq_ctx[idx].trigger = NULL;
> > +	}
> > +
> > +	if (fd < 0)
> > +		return 0;
> > +
> > +	feature->irq_ctx[idx].name =
> > +		kasprintf(GFP_KERNEL, "fpga-irq[%u](%s-%llx)", idx,
> > +			  dev_name(&pdev->dev),
> > +			  (unsigned long long)feature->id);
> > +	if (!feature->irq_ctx[idx].name)
> > +		return -ENOMEM;
> > +
> > +	trigger = eventfd_ctx_fdget(fd);
> > +	if (IS_ERR(trigger)) {
> > +		ret = PTR_ERR(trigger);
> > +		goto free_name;
> > +	}
> > +
> > +	ret = request_irq(irq, dfl_irq_handler, 0,
> > +			  feature->irq_ctx[idx].name, trigger);
> > +	if (!ret) {
> > +		feature->irq_ctx[idx].trigger = trigger;
> > +		return ret;
> > +	}
> > +
> > +	eventfd_ctx_put(trigger);
> > +free_name:
> > +	kfree(feature->irq_ctx[idx].name);
> > +
> > +	return ret;
> > +}
> > +
> > +/**
> > + * dfl_fpga_set_irq_triggers - set eventfd triggers for dfl feature interrupts
> > + *
> > + * @feature: dfl sub feature.
> > + * @start: start of irq index in this dfl sub feature.
> > + * @count: number of irqs.
> > + * @fds: eventfds to bind with irqs. unbind related irq if fds[n] is negative.
> > + *	 unbind "count" specified number of irqs if fds ptr is NULL.
> > + *
> > + * Bind given eventfds with irqs in this dfl sub feature. Unbind related irq if
> > + * fds[n] is negative. Unbind "count" specified number of irqs if fds ptr is
> > + * NULL.
> > + *
> > + * Return: 0 on success, negative error code otherwise.
> > + */
> > +int dfl_fpga_set_irq_triggers(struct dfl_feature *feature, unsigned int start,
> > +			      unsigned int count, int32_t *fds)
> > +{
> > +	unsigned int i;
> > +	int ret = 0;
> > +
> > +	if (start + count < start || start + count > feature->nr_irqs)
> > +		return -EINVAL;
> Up to you, but have you considered to break up the condition above into
> two if () ?

I think maybe we could keep this. The 2 conditions are all for start &
count check, that's why I prefer to put them in one code block.

Thanks,
Yilun.

> > +
> > +	for (i = 0; i < count; i++) {
> > +		int fd = fds ? fds[i] : -1;
> > +
> > +		ret = do_set_irq_trigger(feature, start + i, fd);
> > +		if (ret) {
> > +			while (i--)
> > +				do_set_irq_trigger(feature, start + i, -1);
> > +			break;
> > +		}
> > +	}
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(dfl_fpga_set_irq_triggers);
> > +
> > +/**
> > + * dfl_feature_ioctl_get_num_irqs - dfl feature _GET_IRQ_NUM ioctl interface.
> > + * @pdev: the feature device which has the sub feature
> > + * @feature: the dfl sub feature
> > + * @arg: ioctl argument
> > + *
> > + * Return: 0 on success, negative error code otherwise.
> > + */
> > +long dfl_feature_ioctl_get_num_irqs(struct platform_device *pdev,
> > +				    struct dfl_feature *feature,
> > +				    unsigned long arg)
> > +{
> > +	return put_user(feature->nr_irqs, (__u32 __user *)arg);
> > +}
> > +EXPORT_SYMBOL_GPL(dfl_feature_ioctl_get_num_irqs);
> > +
> > +/**
> > + * dfl_feature_ioctl_set_irq - dfl feature _SET_IRQ ioctl interface.
> > + * @pdev: the feature device which has the sub feature
> > + * @feature: the dfl sub feature
> > + * @arg: ioctl argument
> > + *
> > + * Return: 0 on success, negative error code otherwise.
> > + */
> > +long dfl_feature_ioctl_set_irq(struct platform_device *pdev,
> > +			       struct dfl_feature *feature,
> > +			       unsigned long arg)
> > +{
> > +	struct dfl_feature_platform_data *pdata = dev_get_platdata(&pdev->dev);
> > +	struct dfl_fpga_irq_set hdr;
> > +	s32 *fds;
> > +	long ret;
> > +
> > +	if (!feature->nr_irqs)
> > +		return -ENOENT;
> > +
> > +	if (copy_from_user(&hdr, (void __user *)arg, sizeof(hdr)))
> > +		return -EFAULT;
> > +
> > +	if (!hdr.count || (hdr.start + hdr.count > feature->nr_irqs) ||
> > +	    (hdr.start + hdr.count < hdr.start))
> > +		return -EINVAL;
> > +
> > +	fds = memdup_user((void __user *)(arg + sizeof(hdr)),
> > +			  hdr.count * sizeof(s32));
> > +	if (IS_ERR(fds))
> > +		return PTR_ERR(fds);
> > +
> > +	mutex_lock(&pdata->lock);
> > +	ret = dfl_fpga_set_irq_triggers(feature, hdr.start, hdr.count, fds);
> > +	mutex_unlock(&pdata->lock);
> > +
> > +	kfree(fds);
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(dfl_feature_ioctl_set_irq);
> > +
> >  static void __exit dfl_fpga_exit(void)
> >  {
> >  	dfl_chardev_uinit();
> > diff --git a/drivers/fpga/dfl.h b/drivers/fpga/dfl.h
> > index 4bc165f..f7a8c59 100644
> > --- a/drivers/fpga/dfl.h
> > +++ b/drivers/fpga/dfl.h
> > @@ -17,7 +17,9 @@
> >  #include <linux/bitfield.h>
> >  #include <linux/cdev.h>
> >  #include <linux/delay.h>
> > +#include <linux/eventfd.h>
> >  #include <linux/fs.h>
> > +#include <linux/interrupt.h>
> >  #include <linux/iopoll.h>
> >  #include <linux/io-64-nonatomic-lo-hi.h>
> >  #include <linux/platform_device.h>
> > @@ -213,14 +215,19 @@ struct dfl_feature_driver {
> >   * struct dfl_feature_irq_ctx - dfl private feature interrupt context
> >   *
> >   * @irq: Linux IRQ number of this interrupt.
> > + * @trigger: eventfd context to signal when interrupt happens.
> > + * @name: irq name needed when requesting irq.
> >   */
> >  struct dfl_feature_irq_ctx {
> >  	int irq;
> > +	struct eventfd_ctx *trigger;
> > +	char *name;
> >  };
> >  
> >  /**
> >   * struct dfl_feature - sub feature of the feature devices
> >   *
> > + * @dev: ptr to pdev of the feature device which has the sub feature.
> >   * @id: sub feature id.
> >   * @resource_index: each sub feature has one mmio resource for its registers.
> >   *		    this index is used to find its mmio resource from the
> > @@ -231,6 +238,7 @@ struct dfl_feature_irq_ctx {
> >   * @ops: ops of this sub feature.
> >   */
> >  struct dfl_feature {
> > +	struct platform_device *dev;
> >  	u64 id;
> >  	int resource_index;
> >  	void __iomem *ioaddr;
> > @@ -506,4 +514,13 @@ int dfl_fpga_cdev_release_port(struct dfl_fpga_cdev *cdev, int port_id);
> >  int dfl_fpga_cdev_assign_port(struct dfl_fpga_cdev *cdev, int port_id);
> >  void dfl_fpga_cdev_config_ports_pf(struct dfl_fpga_cdev *cdev);
> >  int dfl_fpga_cdev_config_ports_vf(struct dfl_fpga_cdev *cdev, int num_vf);
> > +int dfl_fpga_set_irq_triggers(struct dfl_feature *feature, unsigned int start,
> > +			      unsigned int count, int32_t *fds);
> > +long dfl_feature_ioctl_get_num_irqs(struct platform_device *pdev,
> > +				    struct dfl_feature *feature,
> > +				    unsigned long arg);
> > +long dfl_feature_ioctl_set_irq(struct platform_device *pdev,
> > +			       struct dfl_feature *feature,
> > +			       unsigned long arg);
> > +
> >  #endif /* __FPGA_DFL_H */
> > diff --git a/include/uapi/linux/fpga-dfl.h b/include/uapi/linux/fpga-dfl.h
> > index ec70a0746..7331350 100644
> > --- a/include/uapi/linux/fpga-dfl.h
> > +++ b/include/uapi/linux/fpga-dfl.h
> > @@ -151,6 +151,19 @@ struct dfl_fpga_port_dma_unmap {
> >  
> >  #define DFL_FPGA_PORT_DMA_UNMAP		_IO(DFL_FPGA_MAGIC, DFL_PORT_BASE + 4)
> >  
> > +/**
> > + * struct dfl_fpga_irq_set - the argument for DFL_FPGA_XXX_SET_IRQ ioctl.
> > + *
> > + * @start: Index of the first irq.
> > + * @count: The number of eventfd handler.
> > + * @evtfds: Eventfd handlers.
> > + */
> > +struct dfl_fpga_irq_set {
> > +	__u32 start;
> > +	__u32 count;
> > +	__s32 evtfds[];
> > +};
> > +
> >  /* IOCTLs for FME file descriptor */
> >  
> >  /**
> > -- 
> > 2.7.4
> > 
> Thanks,
> Moritz

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