linux-kernel - RE: [PATCH v17 2/3] vfio/pci: rename and export range_intesect

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Date: Thu, 8 Feb 2024 06:19:11 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: "ankita@...dia.com" <ankita@...dia.com>, "jgg@...dia.com"
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Subject: RE: [PATCH v17 2/3] vfio/pci: rename and export range_intesect_range

> From: ankita@...dia.com <ankita@...dia.com>
> Sent: Tuesday, February 6, 2024 7:01 AM
> 
> From: Ankit Agrawal <ankita@...dia.com>
> 
> range_intesect_range determines an overlap between two ranges. If an

s/intesect/intersect/

> overlap, the helper function returns the overlapping offset and size.
> 
> The VFIO PCI variant driver emulates the PCI config space BAR offset
> registers. These offset may be accessed for read/write with a variety
> of lengths including sub-word sizes from sub-word offsets. The driver
> makes use of this helper function to read/write the targeted part of
> the emulated register.
> 
> Make this a vfio_pci_core function, rename and export as GPL. Also
> update references in virtio driver.
> 
> Signed-off-by: Ankit Agrawal <ankita@...dia.com>
> ---
>  drivers/vfio/pci/vfio_pci_config.c | 45 +++++++++++++++++++
>  drivers/vfio/pci/virtio/main.c     | 72 +++++++++++-------------------
>  include/linux/vfio_pci_core.h      |  5 +++
>  3 files changed, 76 insertions(+), 46 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_config.c
> b/drivers/vfio/pci/vfio_pci_config.c
> index 672a1804af6a..4fc3c605af13 100644
> --- a/drivers/vfio/pci/vfio_pci_config.c
> +++ b/drivers/vfio/pci/vfio_pci_config.c
> @@ -1966,3 +1966,48 @@ ssize_t vfio_pci_config_rw(struct
> vfio_pci_core_device *vdev, char __user *buf,
> 
>  	return done;
>  }
> +
> +/**
> + * vfio_pci_core_range_intersect_range() - Determine overlap between a
> buffer
> + *					   and register offset ranges.
> + * @range1_start:    start offset of the buffer
> + * @count1:	     number of buffer bytes.
> + * @range2_start:    start register offset
> + * @count2:	     number of bytes of register
> + * @start_offset:    start offset of overlap start in the buffer
> + * @intersect_count: number of overlapping bytes
> + * @register_offset: start offset of overlap start in register
> + *
> + * The function determines an overlap between a register and a buffer.
> + * range1 represents the buffer and range2 represents register.
> + *
> + * Returns: true if there is overlap, false if not.
> + * The overlap start and range is returned through function args.
> + */
> +bool vfio_pci_core_range_intersect_range(loff_t range1_start, size_t count1,
> +					 loff_t range2_start, size_t count2,
> +					 loff_t *start_offset,
> +					 size_t *intersect_count,
> +					 size_t *register_offset)

based on description it's probably clearer to rename:

range1_start -> buf_start
count1 -> buf_cnt
range2_start -> reg_start
count2 -> reg_cnt
start_offset -> buf_offset

but not big deal, so:

Reviewed-by: Kevin Tian <kevin.tian@...el.com>