Re: [PATCH 1/2] staging: ion: Add ion-physmem driver

[Paul Bolle <pebolle@tiscali.nl>]

This patch adds a mismatch between the Kconfig symbol (a bool) and the
code (which suggests it could be built modular too).

On Mon, 2015-04-06 at 18:58 +0300, Andrew Andrianov wrote:
> +config ION_PHYSMEM
> +	bool "Generic PhysMem ION driver"
> +	depends on ION
> +	help
> +	  Provides a generic ION driver that registers the
> +	  /dev/ion device with heaps from devicetree entries.
> +	  This heaps are made of chunks of physical memory

> --- a/drivers/staging/android/ion/Makefile
> +++ b/drivers/staging/android/ion/Makefile

> -obj-$(CONFIG_ION_DUMMY) += ion_dummy_driver.o
> -obj-$(CONFIG_ION_TEGRA) += tegra/
> +obj-$(CONFIG_ION_DUMMY)   += ion_dummy_driver.o
> +obj-$(CONFIG_ION_PHYSMEM) += ion_physmem.o
> +obj-$(CONFIG_ION_TEGRA)   += tegra/

To make absolutely sure I'm reading this correctly: there's no way
ion_physmem.o can ever be part of a module, right?

(If I'm not reading this correctly you can stop reading here.)

> --- /dev/null
> +++ b/drivers/staging/android/ion/ion_physmem.c
> @@ -0,0 +1,237 @@
> +/*
> + * Copyright (C) 2015 RC Module
> + * Andrew Andrianov <andrew@ncrmnt.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * Generic devicetree physmem driver for ION Memory Manager
> + *
> + */

> +#include <linux/module.h>

If this file can only be built-in this include might not be needed.

> +MODULE_DEVICE_TABLE(of, of_match_table);

MODULE_DEVICE_TABLE will always be preprocessed away for built-in code
(see include/linux/module.h).

> +static int ion_physmem_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +	u32 ion_heap_id, ion_heap_align, ion_heap_type;
> +	ion_phys_addr_t addr;
> +	size_t size = 0;
> +	const char *ion_heap_name;
> +	struct resource *res;
> +	struct physmem_ion_dev *ipdev;
> +
> +	/*
> +	   Looks like we can only have one ION device in our system.
> +	   Therefore we call ion_device_create on first probe and only
> +	   add heaps to it on subsequent probe calls.
> +	   FixMe: Do we need to hold a spinlock here once device probing
> +	   becomes async?
> +	*/
> +
> +	if (!idev) {
> +		idev = ion_device_create(ion_physmem_custom_ioctl);
> +		dev_info(&pdev->dev, "ion-physmem: ION PhysMem Driver. (c) RC Module 2015\n");
> +		if (!idev)
> +			return -ENOMEM;
> +	}
> +
> +	ipdev = kzalloc(sizeof(struct physmem_ion_dev), GFP_KERNEL);
> +	if (!ipdev)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, ipdev);
> +
> +	ret =  of_property_read_u32(pdev->dev.of_node, "ion-heap-id",
> +				    &ion_heap_id);
> +	if (ret != 0)
> +		goto errfreeipdev;
> +
> +	ret =  of_property_read_u32(pdev->dev.of_node, "ion-heap-type",
> +				    &ion_heap_type);
> +	if (ret != 0)
> +		goto errfreeipdev;
> +
> +	ret =  of_property_read_u32(pdev->dev.of_node, "ion-heap-align",
> +				    &ion_heap_align);
> +	if (ret != 0)
> +		goto errfreeipdev;
> +
> +	ret =  of_property_read_string(pdev->dev.of_node, "ion-heap-name",
> +				       &ion_heap_name);
> +	if (ret != 0)
> +		goto errfreeipdev;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "memory");
> +	/* Not always needed, throw no error if missing */
> +	if (res) {
> +		/* Fill in some defaults */
> +		addr = res->start;
> +		size = resource_size(res);
> +	}
> +
> +	switch (ion_heap_type) {
> +	case ION_HEAP_TYPE_DMA:
> +		if (res) {
> +			ret = dma_declare_coherent_memory(&pdev->dev,
> +							  res->start,
> +							  res->start,
> +							  resource_size(res),
> +							  DMA_MEMORY_MAP |
> +							  DMA_MEMORY_EXCLUSIVE);
> +			if (ret == 0) {
> +				ret = -ENODEV;
> +				goto errfreeipdev;
> +			}
> +		}
> +		/*
> +		 *  If no memory region declared in dt we assume that
> +		 *  the user is okay with plain dma_alloc_coherent.
> +		 */
> +		break;
> +	case ION_HEAP_TYPE_CARVEOUT:
> +	case ION_HEAP_TYPE_CHUNK:
> +	{
> +		if (size == 0) {
> +			ret = -EIO;
> +			goto errfreeipdev;
> +		}
> +		ipdev->freepage_ptr = alloc_pages_exact(size, GFP_KERNEL);
> +		if (ipdev->freepage_ptr) {
> +			addr = virt_to_phys(ipdev->freepage_ptr);
> +		} else {
> +			ret = -ENOMEM;
> +			goto errfreeipdev;
> +		}
> +		break;
> +	}
> +	}
> +
> +	ipdev->data.id    = ion_heap_id;
> +	ipdev->data.type  = ion_heap_type;
> +	ipdev->data.name  = ion_heap_name;
> +	ipdev->data.align = ion_heap_align;
> +	ipdev->data.base  = addr;
> +	ipdev->data.size  = size;
> +	/* This one make dma_declare_coherent_memory actually work */
> +	ipdev->data.priv  = &pdev->dev;
> +
> +
> +	ipdev->heap = ion_heap_create(&ipdev->data);
> +	if (!ipdev->heap)
> +		goto errfreeipdev;
> +
> +	if (!try_module_get(THIS_MODULE))
> +		goto errfreeheap;

For built-in only code THIS_MODULE will be, basically, always NULL. So,
I think try_module_get() will always return true.

> +	ion_device_add_heap(idev, ipdev->heap);
> +
> +	dev_info(&pdev->dev, "ion-physmem: heap %s id %d type %d align 0x%x at phys 0x%lx len %lu KiB\n",
> +	       ion_heap_name, ion_heap_id, ion_heap_type, ion_heap_align,
> +	       (unsigned long int) addr, ((unsigned long int) size / 1024));
> +
> +	return 0;
> +
> +errfreeheap:
> +	kfree(ipdev->heap);
> +errfreeipdev:
> +	kfree(ipdev);
> +	return -ENOMEM;
> +}
> +
> +static int ion_physmem_remove(struct platform_device *pdev)
> +{
> +	struct physmem_ion_dev *ipdev = platform_get_drvdata(pdev);
> +
> +	ion_heap_destroy(ipdev->heap);
> +	if (ipdev->need_free_coherent)
> +		dma_release_declared_memory(&pdev->dev);
> +	if (ipdev->freepage_ptr)
> +		free_pages_exact(ipdev->freepage_ptr, ipdev->data.size);
> +	kfree(ipdev->heap);
> +	kfree(ipdev);
> +	module_put(THIS_MODULE);

Again, THIS_MODULE will be, basically, always NULL.

> +	return 0;
> +}
> +
> +static struct platform_driver ion_physmem_driver = {
> +	.probe		= ion_physmem_probe,
> +	.remove		= ion_physmem_remove,
> +	.driver		= {
> +		.owner	= THIS_MODULE,

Ditto.

> +		.name	= "ion-physmem",
> +		.of_match_table = of_match_ptr(of_match_table),
> +	},
> +};
> +module_platform_driver(ion_physmem_driver);

For built-in only code this is equivalent to, if I remember correctly,
having a small wrapper call
    platform_driver_register(&ion_physmem_driver);

and mark that wrapper with device_initcall().

> +MODULE_DESCRIPTION("Generic physmem driver for ION");
> +MODULE_AUTHOR("Andrew Andrianov <andrew@ncrmnt.org>");
> +MODULE_LICENSE("GPL");

These macros will always be effectively preprocessed away for built-in
only code.

(If you plan to make ION_PHYSMEM tristate, you should note that "GPL"
doesn't match the license stated in the comment at the top of this file,
see include/linux/module.h.)


Paul Bolle