2015-07-24 8:20 GMT+09:00 Simon Glass sjg@chromium.org:
Hi Masahiro,
On 23 July 2015 at 00:17, Masahiro Yamada yamada.masahiro@socionext.com wrote:
In U-Boot's driver model, memory is basically allocated and freed in the core framework. So, low level drivers generally only have to specify the size of needed memory with .priv_auto_alloc_size, .platdata_auto_alloc_size, etc. Nevertheless, some drivers still need to allocate/free memory on their own in case they cannot statically know the necessary memory size. So, I believe it is reasonable enough to port Devres into U-boot.
Devres, which originates in Linux, manages device resources for each device and automatically releases them on driver detach. With devres, device resources are guaranteed to be freed whether initialization fails half-way or the device gets detached.
The basic idea is totally the same to that of Linux, but I tweaked it a bit so that it fits in U-Boot's driver model.
In U-Boot, drivers are activated in two steps: binding and probing. Binding puts a driver and a device together. It is just data manipulation on the system memory, so nothing has happened on the hardware device at this moment. When the device is really used, it is probed. Probing initializes the real hardware device to make it really ready for use.
So, the resources acquired during the probing process must be freed when the device is removed. Likewise, what has been allocated in binding should be released when the device is unbound. The struct devres has a member "probe" to remember when the resource was allocated.
CONFIG_DEBUG_DEVRES is also supported for easier debugging. If enabled, debug messages are printed each time a resource is allocated/freed.
Signed-off-by: Masahiro Yamada yamada.masahiro@socionext.com
Please can you add comments for these fields? I'm not sure what dr_release_t is for, for exable.
OK, I commented this structure in v4.
The dr_release_t is a callback that is automatically invoked when the resource is freed.
This callback should do the opposite action to the allocator.
For example, devm_ioremap() calls iounmap() in the release callback, devm_clk_get() calls clk_put() in the release callback, etc.
+struct devres {
struct list_head entry;dr_release_t release;bool probe;+#ifdef CONFIG_DEBUG_DEVRES
const char *name;size_t size;+#endif
unsigned long long data[];+};
+static void release_nodes(struct udevice *dev, struct list_head *head,
bool probe_only)+{
struct devres *dr, *tmp;list_for_each_entry_safe_reverse(dr, tmp, head, entry) {if (probe_only && !dr->probe)break;devres_log(dev, dr, "REL");dr->release(dev, dr->data);Somewhere in the header file can you please explain the use case for the release() method?
I explained above, but I am not sure if it should be explained in the header file. Such a thing is generally explained in a README. Uh, I am too laze to write a README...
But you can find one in Linux: Documentation/driver-modeol/devres.txt
And, use cases are everywhere in the kernel code.