Re: [PATCH v2 5/6] staging: vc04_services: Drop global variables tracking allocated pages

[Kieran Bingham <kieran.bingham@ideasonboard.com>]

Quoting Umang Jain (2024-03-14 10:06:06)
> The variables tracking allocated pages fragments in vchiq_arm.c
> can be easily moved to struct vchiq_drvdata instead of being global.
> This helps us to drop the non-essential global variables in the vchiq
> interface.
> 
> Drop the TODO item as well, as it is now totally addressed:
> > Get rid of all non essential global structures and create a proper per
>   device structure
> 
> No functional changes intended in this patch.
> 
> Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> ---
>  drivers/staging/vc04_services/interface/TODO  |  8 ---
>  .../interface/vchiq_arm/vchiq_arm.c           | 53 +++++++++----------
>  .../interface/vchiq_arm/vchiq_arm.h           |  6 +++
>  3 files changed, 30 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/staging/vc04_services/interface/TODO b/drivers/staging/vc04_services/interface/TODO
> index 05eb5140d096..15f12b8f213e 100644
> --- a/drivers/staging/vc04_services/interface/TODO
> +++ b/drivers/staging/vc04_services/interface/TODO
> @@ -41,14 +41,6 @@ The code follows the 80 characters limitation yet tends to go 3 or 4 levels of
>  indentation deep making it very unpleasant to read. This is specially relevant
>  in the character driver ioctl code and in the core thread functions.
>  
> -* Get rid of all non essential global structures and create a proper per
> -device structure
> -
> -The first thing one generally sees in a probe function is a memory allocation
> -for all the device specific data. This structure is then passed all over the
> -driver. This is good practice since it makes the driver work regardless of the
> -number of devices probed.
> -
>  * Clean up Sparse warnings from __user annotations. See
>  vchiq_irq_queue_bulk_tx_rx(). Ensure that the address of "&waiter->bulk_waiter"
>  is never disclosed to userspace.
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> index 282f83b335d4..666ab73ce0d1 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> @@ -140,12 +140,6 @@ struct vchiq_pagelist_info {
>  };
>  
>  static void __iomem *g_regs;

What happens with this one ? Is it essential to be global? Can it be
part of the device? Who's mapping it? or unmapping?

If we're keeping it global, I'd add a comment...

> -static unsigned int g_fragments_size;
> -static char *g_fragments_base;
> -static char *g_free_fragments;
> -static struct semaphore g_free_fragments_sema;
> -
> -static DEFINE_SEMAPHORE(g_free_fragments_mutex, 1);
>  
>  static int
>  vchiq_blocking_bulk_transfer(struct vchiq_instance *instance, unsigned int handle, void *data,
> @@ -376,20 +370,20 @@ create_pagelist(struct vchiq_instance *instance, char *buf, char __user *ubuf,
>             (drvdata->cache_line_size - 1)))) {
>                 char *fragments;
>  
> -               if (down_interruptible(&g_free_fragments_sema)) {
> +               if (down_interruptible(&drvdata->free_fragments_sema)) {
>                         cleanup_pagelistinfo(instance, pagelistinfo);
>                         return NULL;
>                 }
>  
> -               WARN_ON(!g_free_fragments);
> +               WARN_ON(!drvdata->free_fragments);
>  
> -               down(&g_free_fragments_mutex);
> -               fragments = g_free_fragments;
> +               down(&drvdata->free_fragments_mutex);
> +               fragments = drvdata->free_fragments;
>                 WARN_ON(!fragments);
> -               g_free_fragments = *(char **)g_free_fragments;
> -               up(&g_free_fragments_mutex);
> +               drvdata->free_fragments = *(char **)drvdata->free_fragments;
> +               up(&drvdata->free_fragments_mutex);
>                 pagelist->type = PAGELIST_READ_WITH_FRAGMENTS +
> -                       (fragments - g_fragments_base) / g_fragments_size;
> +                       (fragments - drvdata->fragments_base) / drvdata->fragments_size;
>         }
>  
>         return pagelistinfo;
> @@ -421,10 +415,10 @@ free_pagelist(struct vchiq_instance *instance, struct vchiq_pagelist_info *pagel
>         pagelistinfo->scatterlist_mapped = 0;
>  
>         /* Deal with any partial cache lines (fragments) */
> -       if (pagelist->type >= PAGELIST_READ_WITH_FRAGMENTS && g_fragments_base) {
> -               char *fragments = g_fragments_base +
> +       if (pagelist->type >= PAGELIST_READ_WITH_FRAGMENTS && drvdata->fragments_base) {
> +               char *fragments = drvdata->fragments_base +
>                         (pagelist->type - PAGELIST_READ_WITH_FRAGMENTS) *
> -                       g_fragments_size;
> +                       drvdata->fragments_size;
>                 int head_bytes, tail_bytes;
>  
>                 head_bytes = (cache_line_size - pagelist->offset) &
> @@ -449,11 +443,11 @@ free_pagelist(struct vchiq_instance *instance, struct vchiq_pagelist_info *pagel
>                                 fragments + cache_line_size,
>                                 tail_bytes);
>  
> -               down(&g_free_fragments_mutex);
> -               *(char **)fragments = g_free_fragments;
> -               g_free_fragments = fragments;
> -               up(&g_free_fragments_mutex);
> -               up(&g_free_fragments_sema);
> +               down(&drvdata->free_fragments_mutex);
> +               *(char **)fragments = drvdata->free_fragments;
> +               drvdata->free_fragments = fragments;
> +               up(&drvdata->free_fragments_mutex);
> +               up(&drvdata->free_fragments_sema);
>         }
>  
>         /* Need to mark all the pages dirty. */
> @@ -489,11 +483,11 @@ static int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state
>         if (err < 0)
>                 return err;
>  
> -       g_fragments_size = 2 * drvdata->cache_line_size;
> +       drvdata->fragments_size = 2 * drvdata->cache_line_size;
>  
>         /* Allocate space for the channels in coherent memory */
>         slot_mem_size = PAGE_ALIGN(TOTAL_SLOTS * VCHIQ_SLOT_SIZE);
> -       frag_mem_size = PAGE_ALIGN(g_fragments_size * MAX_FRAGMENTS);
> +       frag_mem_size = PAGE_ALIGN(drvdata->fragments_size * MAX_FRAGMENTS);
>  
>         slot_mem = dmam_alloc_coherent(dev, slot_mem_size + frag_mem_size,
>                                        &slot_phys, GFP_KERNEL);
> @@ -513,15 +507,16 @@ static int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state
>         vchiq_slot_zero->platform_data[VCHIQ_PLATFORM_FRAGMENTS_COUNT_IDX] =
>                 MAX_FRAGMENTS;
>  
> -       g_fragments_base = (char *)slot_mem + slot_mem_size;
> +       drvdata->fragments_base = (char *)slot_mem + slot_mem_size;
>  
> -       g_free_fragments = g_fragments_base;
> +       drvdata->free_fragments = drvdata->fragments_base;
>         for (i = 0; i < (MAX_FRAGMENTS - 1); i++) {
> -               *(char **)&g_fragments_base[i * g_fragments_size] =
> -                       &g_fragments_base[(i + 1) * g_fragments_size];
> +               *(char **)&drvdata->fragments_base[i * drvdata->fragments_size] =
> +                       &drvdata->fragments_base[(i + 1) * drvdata->fragments_size];
>         }
> -       *(char **)&g_fragments_base[i * g_fragments_size] = NULL;
> -       sema_init(&g_free_fragments_sema, MAX_FRAGMENTS);
> +       *(char **)&drvdata->fragments_base[i * drvdata->fragments_size] = NULL;
> +       sema_init(&drvdata->free_fragments_sema, MAX_FRAGMENTS);
> +       sema_init(&drvdata->free_fragments_mutex, 1);
>  
>         err = vchiq_init_state(state, vchiq_slot_zero, dev);
>         if (err)
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h
> index f2fd572df2b3..d5c0a8e9fa2b 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h
> @@ -34,6 +34,12 @@ struct vchiq_drvdata {
>         struct rpi_firmware *fw;
>  
>         struct vchiq_connected drv_connected;
> +
> +       struct semaphore free_fragments_sema;
> +       struct semaphore free_fragments_mutex;
> +       char *fragments_base;
> +       char *free_fragments;
> +       unsigned int fragments_size;
>  };
>  
>  struct user_service {
> -- 
> 2.43.0
>