Re: [PATCH] Add new uio device for PCI with dynamic memory allocation

[Dan Carpenter]

Looks good.  A couple minor comments below.

On Mon, Oct 02, 2017 at 03:02:09PM +0000, Stahl, Manuel wrote:
> +static int open(struct uio_info *info, struct inode *inode)
> +{
> +	struct uio_pci_dmem_dev *priv = to_uio_pci_dmem_dev(info);
> +	struct uio_mem *uiomem;
> +	int ret = 0;
> +	int dmem_region = 0;
> +
> +	uiomem = &priv->info.mem[dmem_region];
> +
> +	mutex_lock(&priv->alloc_lock);
> +	while (!priv->refcnt && uiomem < &priv->info.mem[MAX_UIO_MAPS]) {
> +		void *addr;
> +
> +		if (!uiomem->size)
> +			break;
> +
> +		addr = dma_alloc_coherent(&priv->pdev->dev, uiomem->size,
> +					  (dma_addr_t *)&uiomem->addr,
> +					  GFP_KERNEL);
> +		if (!addr)
> +			uiomem->addr = DMEM_MAP_ERROR;
> +
> +		priv->dmem_region_vaddr[dmem_region++] = addr;
> +		++uiomem;
> +	}
> +	if (pci_check_and_mask_intx(priv->pdev))
> +		dev_info(&priv->pdev->dev, "Found pending interrupt");
> +
> +	if (!priv->refcnt)
> +		pci_set_master(priv->pdev);
> +
> +	priv->refcnt++;
> +
> +	mutex_unlock(&priv->alloc_lock);
> +
> +	return ret;

Just "return 0;" is more readable/explicit than "return ret;".

> +}
> +
> +static int release(struct uio_info *info, struct inode *inode)
> +{
> +	struct uio_pci_dmem_dev *priv = to_uio_pci_dmem_dev(info);
> +	struct uio_mem *uiomem;
> +	int dmem_region = 0;
> +
> +	uiomem = &priv->info.mem[dmem_region];
> +
> +	mutex_lock(&priv->alloc_lock);
> +
> +	priv->refcnt--;
> +	while (!priv->refcnt && uiomem < &priv->info.mem[MAX_UIO_MAPS]) {
> +		if (!uiomem->size)
> +			break;

I think this needs to be a continue instead of a break to match
parse_dmem_entries() since we don't break for size == 0 in that loop.

> +		if (priv->dmem_region_vaddr[dmem_region]) {
> +			dma_free_coherent(&priv->pdev->dev, uiomem->size,
> +					  priv->dmem_region_vaddr[dmem_region],
> +					  uiomem->addr);
> +		}
> +		uiomem->addr = DMEM_MAP_ERROR;
> +		++dmem_region;
> +		++uiomem;
> +	}
> +	if (pci_check_and_mask_intx(priv->pdev))
> +		dev_info(&priv->pdev->dev, "Found pending interrupt");
> +
> +	if (!priv->refcnt)
> +		pci_clear_master(priv->pdev);
> +
> +	mutex_unlock(&priv->alloc_lock);
> +	return 0;
> +}
> +
> +static int dmem_mmap(struct uio_info *info, struct vm_area_struct *vma)
> +{
> +	struct uio_pci_dmem_dev *gdev = to_uio_pci_dmem_dev(info->priv);
> +	struct uio_mem *uiomem;
> +	int mi = vma->vm_pgoff;
> +
> +	if (mi >= MAX_UIO_MAPS)
> +		return -EINVAL;
> +
> +	uiomem = &info->mem[mi];
> +	if (uiomem->memtype != UIO_MEM_PHYS)
> +		return -EINVAL;
> +	if (!uiomem->size)
> +		return -EINVAL;
> +
> +	/* DMA address */
> +	vma->vm_pgoff = 0;
> +	return dma_mmap_coherent(&gdev->pdev->dev, vma,
> +				 gdev->dmem_region_vaddr[mi],
> +				 uiomem->addr, uiomem->size);
> +}
> +
> +/* Interrupt handler. Read/modify/write the command register to disable the
> + * interrupt.
> + */
> +static irqreturn_t irqhandler(int irq, struct uio_info *info)
> +{
> +	struct uio_pci_dmem_dev *gdev = to_uio_pci_dmem_dev(info);
> +
> +	if (gdev->pdev->msi_enabled)
> +		return IRQ_HANDLED;
> +
> +	if (pci_check_and_mask_intx(gdev->pdev))
> +		return IRQ_HANDLED;
> +
> +	return IRQ_NONE;
> +}
> +
> +static unsigned int uio_dmem_dma_bits = 32;
> +static char uio_dmem_sizes[256];
> +
> +static int parse_dmem_entries(struct pci_dev *pdev,
> +			      const struct pci_device_id *id,
> +			      struct uio_pci_dmem_dev *gdev)
> +{
> +	int ret;
> +	u32 regions = 0;
> +	u32 vendor, device;
> +	char *s, *tok, *sizes = NULL;
> +	unsigned long long size;
> +	struct uio_mem *uiomem;
> +	char * const buf = kstrdup(uio_dmem_sizes, GFP_KERNEL);
> +
> +	if (!buf) {
> +		ret = -ENOMEM;
> +		return ret;

I wish you wouldn't put the allocation in the declaration block...
Declaration blocks are a larger than expected source of static checker
bugs so I think they are not reviewed as carefully.  Anyway just do
"return -ENOMEM;" here instead of using a temporary variable.

> +	}
> +
> +	/* Find-out start and end of sizes list */
> +	s = buf;
> +	while (*s != '\0') {
> +		sizes = NULL;
> +		tok = strsep(&s, ":");
> +		if (!tok)
> +			break;
> +		ret = kstrtou32(tok, 16, &vendor);
> +		if (ret)
> +			break;
> +		tok = strsep(&s, ":");
> +		if (!tok)
> +			break;
> +		ret = kstrtou32(tok, 16, &device);
> +		if (ret)
> +			break;
> +		sizes = strsep(&s, ";");
> +		if (vendor == id->vendor && device == id->device)
> +			break;
> +	}
> +
> +	memset(gdev->info.mem, 0, sizeof(gdev->info.mem));
> +	if (sizes) {
> +		dev_info(&pdev->dev, "Regions: %s\n", sizes);
> +
> +		/* Parse dynamic regions from sizes list */
> +		regions = 0;
> +		size = 0;
> +		s = sizes;
> +		while (s && (regions < MAX_UIO_MAPS)) {
> +			tok = strsep(&s, ",");
> +			if (!tok)
> +				break;
> +
> +			size = memparse(tok, NULL);
> +			if (size) {
> +				uiomem = &gdev->info.mem[regions];
> +				uiomem->memtype = UIO_MEM_PHYS;
> +				/* Will be allocated in open() call */
> +				uiomem->addr = DMEM_MAP_ERROR;
> +				uiomem->size = size;
> +				regions++;
> +			}
> +		}
> +		if (s)
> +			dev_warn(&pdev->dev, "device has more than "
> +					__stringify(MAX_UIO_MAPS)
> +					" dynamic memory regions.\n");
> +	}
> +	dev_info(&pdev->dev, "Found %d regions\n", regions);
> +
> +	kfree(buf);
> +	return ret;
> +}
> +
> +static int probe(struct pci_dev *pdev, const struct pci_device_id *id)
> +{
> +	struct uio_pci_dmem_dev *gdev;
> +	int err;
> +
> +	dev_info(&pdev->dev, "Probe %s for %04x:%04x\n", DRIVER_NAME,
> +		 id->vendor, id->device);
> +
> +	err = pci_enable_device(pdev);
> +	if (err) {
> +		dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n",
> +			__func__, err);
> +		return err;
> +	}
> +
> +	dev_info(&pdev->dev, "Legacy IRQ: %i", pdev->irq);
> +	/* Try to use MSI interrupts */
> +	pci_enable_msi_range(pdev, 1, 1);
> +	if (pdev->irq && !pci_intx_mask_supported(pdev)) {
> +		err = -ENODEV;
> +		goto err_disable_pci;
> +	}
> +
> +	gdev = kzalloc(sizeof(*gdev), GFP_KERNEL);
> +	if (!gdev) {
> +		err = -ENOMEM;
> +		goto err_disable_pci;
> +	}
> +
> +	gdev->info.name = DRIVER_NAME;
> +	gdev->info.version = DRIVER_VERSION;
> +	gdev->info.irq = pdev->irq;
> +	gdev->info.irq_flags = IRQF_SHARED;
> +	gdev->info.handler = irqhandler;
> +	gdev->info.open = open;
> +	gdev->info.release = release;
> +	gdev->info.mmap = dmem_mmap;
> +	gdev->info.priv = gdev;
> +	gdev->pdev = pdev;
> +
> +	/* Set DMA coherent mask */
> +	if (uio_dmem_dma_bits > 64)
> +		uio_dmem_dma_bits = 64;
> +	err = dma_set_coherent_mask(&pdev->dev,
> +				    DMA_BIT_MASK(uio_dmem_dma_bits));
> +	if (err) {
> +		dev_err(&pdev->dev, "Unable to dma_set_coherent_mask\n");
> +		goto err_free_gdev;
> +	}
> +
> +	err = parse_dmem_entries(pdev, id, gdev);
> +	if (err)
> +		goto err_free_gdev;
> +
> +	mutex_init(&gdev->alloc_lock);
> +
> +	if (uio_register_device(&pdev->dev, &gdev->info))
> +		goto err_free_gdev;

Preserve the error code from uio_register_device().

> +	pci_set_drvdata(pdev, gdev);
> +
> +	return 0;
> +err_free_gdev:
> +	kfree(gdev);
> +err_disable_pci:
> +	pci_disable_msi(pdev);
> +	pci_disable_device(pdev);
> +	return err;
> +}

regards,
dan carpenter