Thanks for the explanation. Reviewed-by: Mark Zhang <markz@xxxxxxxxxx> Mark On 01/05/2015 10:49 PM, Thierry Reding wrote: > * PGP Signed by an unknown key > > On Tue, Dec 23, 2014 at 03:30:20PM +0800, Mark Zhang wrote: >> On 12/19/2014 11:24 PM, Thierry Reding wrote: >>> From: Thierry Reding <treding@xxxxxxxxxx> >>> >>> Previously the struct bus_type exported by the host1x infrastructure was >>> only a very basic skeleton. Turn that implementation into a more full- >>> fledged bus to support proper probe ordering and power management. >>> >>> Note that the bus infrastructure needs to be available before any of the >>> drivers can be registered, so the bus needs to be registered before the >>> host1x module. Otherwise drivers could be registered before the module >>> is loaded and trigger a BUG_ON() in driver_register(). To ensure the bus >>> infrastructure is always there, always build the code into the kernel >>> when enabled and register it with a postcore initcall. >>> >> >> So this means there is no chance that host1x can be built as a kernel >> module, right? I'm fine with that, just asking. > > No, it means that not all of host1x can be built as a module. The host1x > bus infrastructure will always be built-in when TEGRA_HOST1X is enabled. > >>> Signed-off-by: Thierry Reding <treding@xxxxxxxxxx> >>> --- >> [...] >>> diff --git a/drivers/gpu/host1x/Makefile b/drivers/gpu/host1x/Makefile >>> index c1189f004441..a3e667a1b6f5 100644 >>> --- a/drivers/gpu/host1x/Makefile >>> +++ b/drivers/gpu/host1x/Makefile >>> @@ -1,5 +1,4 @@ >>> host1x-y = \ >>> - bus.o \ >>> syncpt.o \ >>> dev.o \ >>> intr.o \ >>> @@ -13,3 +12,5 @@ host1x-y = \ >>> hw/host1x04.o >>> >>> obj-$(CONFIG_TEGRA_HOST1X) += host1x.o >>> + >>> +obj-y += bus.o >> >> I didn't get it, why we need to do this? > > If CONFIG_TEGRA_HOST1X=m, then obj-$(CONFIG_TEGRA_HOST1X) builds the > bus.o into a module. But we want it to always be built-in. The build > system will descend into the drivers/gpu/host1x directory only if the > TEGRA_HOST1X symbol is selected (either =y or =m), therefore obj-y here > will result in bus.o being built-in whether the rest of host1x is built > as a module or built-in. > >>> diff --git a/drivers/gpu/host1x/bus.c b/drivers/gpu/host1x/bus.c >>> index 0b52f0ea8871..28630a5e9397 100644 >>> --- a/drivers/gpu/host1x/bus.c >>> +++ b/drivers/gpu/host1x/bus.c >>> @@ -72,13 +72,14 @@ static void host1x_subdev_del(struct host1x_subdev *subdev) >> [...] >>> >>> static inline struct host1x_device *to_host1x_device(struct device *dev) >>> >> >> The change looks good to me. Just one thing I feel not comfortable: >> "struct host1x_device" is not a real device, it represents the drm >> device actually. The real tegra host1x device is represented by "struct >> host1x". But the name "host1x_device" makes people confusing, I mean, it >> will make people thinking it's the real "tegra host1x" device then bring >> the reading difficulty. > > The reason behind that name is that host1x provides a bus (real to some > degree, but also virtual). host1x is the device that provides the bus > whereas a host1x_device is a "device" on the "host1x" bus. That's just > like an i2c_client is a "client" on the "I2C" bus. Or an spi_device is a > "device" on the "SPI" bus. > >> Why don't we change this to something like "drm_device" or >> "tegra_drm_device"? > > Other devices can be host1x devices. Some time ago work was being done > on a driver for the CSI/VI hardware (for camera or video input). The > idea was that it would also be instantiated as a host1x_device in some > other subsystem (V4L2 at the time). > > The functionality here is generic and in no way DRM specific. > > Thierry > > * Unknown Key > * 0x7F3EB3A1 > -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
