Hello Yann, On Tue, Jan 14, 2014 at 08:18:29AM +0100, Yann Droneaud wrote: > Since commit 01dcc60a7cb8, platform_device_register_full() is > available to allocate and register a platform device. > > If a dma_mask is provided as part of platform_device_info, > platform_device_register_full() allocate memory for a u64 > using kmalloc(). > > A comment in the code state that "[t]his memory isn't freed > when the device is put". > > It's never a good thing to leak memory, but there's only very > few users of platform_device_info's dma_mask, and those are mostly > "static" devices that are not going to be plugged/unplugged. > > So memory leak is not really an issue, but allocating 8 bytes > through kmalloc() seems overkill, so this patch moves dma_mask > after the platform_device struct, dynamically allocated along > the name buffer. > > With dma_mask part of the memory allocated for the platform_device > struct, like name buffer, it will be released with it: > no memory leak, no small allocation. > > The drawback is the additional code needed to handle > dma_mask allocation: > > Before (on next-20140113 with gcc-4.8): > text data bss dec hex filename > 5600 472 32 6104 17d8 obj-arm/drivers/base/platform.o > 5927 532 32 6491 195b obj-i386/drivers/base/platform.o > 7036 960 48 8044 1f6c obj-x86_64/drivers/base/platform.o > > After: > text data bss dec hex filename > 5668 472 32 6172 181c obj-arm/drivers/base/platform.o > 6007 532 32 6571 19ab obj-i386/drivers/base/platform.o > 7132 960 48 8140 1fcc obj-x86_64/drivers/base/platform.o > > Changes from v1 [1]: > - remove unneeded kfree() from error path > - add reference to author/commit adding allocation of dmamask > > Changes from v0 [2]: > - small rewrite to squeeze the patch to a bare minimal > > [1] > http://lkml.kernel.org/r/1389649085-7365-1-git-send-email-ydrone...@opteya.com > https://patchwork.kernel.org/patch/3480961/ > > [2] > http://lkml.kernel.org/r/1386886207-2735-1-git-send-email-ydrone...@opteya.com > > Cc: Uwe Kleine-König <u.kleine-koe...@pengutronix.de> > Cc: Dmitry Torokhov <dtor_c...@ameritech.net> > Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> > Signed-off-by: Yann Droneaud <ydrone...@opteya.com> > --- > > Hi Greg, > > > Why haven't you cc:ed the author of that comment? He would be best to > > evaluate if this patch is good enough or not. > > > > I must admit I was a bit lazy: I've tried ./script/get_maintainer.pl --git / > --git-blame > but the results scare me, so I've send the patch to the maintainer only. (And > somehow > I've thought you wrote that comment). > > > And is leaking that memory really an issue? As you point out, these > > aren't devices that are going to go away (I'd argue that no platform > > device should ever be a removable device, but that's a longer > > argument...) > > > > I've seen some removable platform driver ... and, in fact, wrote some: > when writing/testing it, being able to remove the devices/driver is a must. > > > Please resend and cc: all of the needed developers. > > > > Thanks for the advice. > > Regards. > > drivers/base/platform.c | 83 > ++++++++++++++++++++++++++++++++++++------------- > 1 file changed, 62 insertions(+), 21 deletions(-) > > diff --git a/drivers/base/platform.c b/drivers/base/platform.c > index 3a94b799f166..6e3e639fb886 100644 > --- a/drivers/base/platform.c > +++ b/drivers/base/platform.c > @@ -157,7 +157,7 @@ EXPORT_SYMBOL_GPL(platform_add_devices); > > struct platform_object { > struct platform_device pdev; > - char name[1]; > + char payload[0]; I don't know the recent minimal versions needed to compile the kernel and since when gcc supports c99 flexible array members, but I would expect that they just work. Having said that I'd prefer using that one, i.e. use char payload[]; > }; > > /** > @@ -186,6 +186,25 @@ static void platform_device_release(struct device *dev) > kfree(pa); > } > > +static struct platform_object *platform_object_alloc(size_t payload) > +{ > + struct platform_object *pa; > + > + pa = kzalloc(sizeof(*pa) + payload, GFP_KERNEL); > + > + return pa; > +} > + > +static void platform_object_init(struct platform_object *pa, > + const char *name, int id) > +{ > + pa->pdev.name = name; > + pa->pdev.id = id; > + device_initialize(&pa->pdev.dev); > + pa->pdev.dev.release = platform_device_release; > + arch_setup_pdev_archdata(&pa->pdev); > +} > + > /** > * platform_device_alloc - create a platform device > * @name: base name of the device we're adding > @@ -198,14 +217,10 @@ struct platform_device *platform_device_alloc(const > char *name, int id) > { > struct platform_object *pa; > > - pa = kzalloc(sizeof(struct platform_object) + strlen(name), GFP_KERNEL); > + pa = platform_object_alloc(strlen(name) + 1); > if (pa) { > - strcpy(pa->name, name); > - pa->pdev.name = pa->name; > - pa->pdev.id = id; > - device_initialize(&pa->pdev.dev); > - pa->pdev.dev.release = platform_device_release; > - arch_setup_pdev_archdata(&pa->pdev); > + strcpy(pa->payload, name); > + platform_object_init(pa, pa->payload, id); > } > > return pa ? &pa->pdev : NULL; > @@ -213,6 +228,39 @@ struct platform_device *platform_device_alloc(const char > *name, int id) > EXPORT_SYMBOL_GPL(platform_device_alloc); > > /** > + * platform_device_dmamask_alloc - create a platform device suitable to hold > a dmamask > + * @name: base name of the device we're adding > + * @id: instance id > + * > + * Create a platform device object which can have other objects attached > + * to it, and which will have attached objects freed when it is released. > + */ > +static struct platform_device *platform_device_dmamask_alloc(const char > *name, > + int id) > +{ > + struct platform_object *pa; > + const size_t padding = (((offsetof(struct platform_object, payload) + > + (__alignof__(u64) - 1)) & > + ~(__alignof__(u64) - 1)) - > + offsetof(struct platform_object, payload)); > + > + pa = platform_object_alloc(padding + sizeof(u64) + strlen(name) + 1); > + if (pa) { > + char *payload = pa->payload + padding; > + /* > + * Conceptually dma_mask in struct device should not be a > pointer. > + * See http://thread.gmane.org/gmane.linux.kernel.pci/9081 > + */ > + pa->pdev.dev.dma_mask = (void *)payload; > + payload += sizeof(u64); > + strcpy(payload, name); > + platform_object_init(pa, payload, id); > + } > + > + return pa ? &pa->pdev : NULL; > +} This looks all complicated. Did you think about spending the extra memory and add a dma_mask to platform_object? That should simplify the code quite a bit which probably is worth the extra memory being used.
Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
