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Date: Tue, 07 Apr 2015 10:35:45 +0200
From: Paul Bolle <pebolle@...cali.nl>
To: Andrew Andrianov <andrew@...mnt.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Arve Hjønnevåg <arve@...roid.com>,
Riley Andrews <riandrews@...roid.com>,
Chen Gang <gang.chen.5i5j@...il.com>,
Fabian Frederick <fabf@...net.be>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] staging: ion: Add ion-physmem driver
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@...mnt.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@...mnt.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
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