[alsa-devel] Why open-coding in sof_hda_bus_init()?

[Pierre-Louis Bossart]

On 5/31/19 12:11 PM, Takashi Iwai wrote:
> Hi,
> 
> while looking at SOF code due to the recent debugging session, I
> noticed that sof_hda_bus_init() is basically an open-code of the
> existing snd_hdac_ext_bus_init().  Why don't we simply call
> snd_hdac_ext_bus_init() like below?

It's intentional.
We've been asked since Day1 of SOF on ApolloLake to provide a 
'self-contained' controller-only support that has no dependency on the 
snd_hdac library for solutions where HDaudio links+codecs are not used 
(typically IOT devices). This was driven by the lack of separation 
between layers in that library as well as a desire to have a 
dual-license. That's why you see the init and some of the basic 
utilities re-implemented for SOF.

However for cases where HDaudio+HDMI are required, we didn't want to 
reinvent the wheel - HDaudio is complicated enough - and do make use of 
this snd_hdac library.

We have a config SND_SOC_SOF_HDA that controls in which mode we operate, 
and it enables HDMI by default (for I2S+HDMI solutions). To get external 
HDaudio codecs you need the additional SOF_HDAUDIO_CODEC kconfig.

Does this help?

> 
> The only thing that differs is the handling of bus->id number, where
> SOF fixes to zero (which was actually done in a patch after the first
> commit).  But judging from the comment, this doesn't seem like a big
> matter, as we assume a single bus, so far...
> 
> 
> thanks,
> 
> Takashi
> 
> ---
> diff --git a/sound/soc/sof/intel/Makefile b/sound/soc/sof/intel/Makefile
> index b8f58e006e29..f42450a9a7b6 100644
> --- a/sound/soc/sof/intel/Makefile
> +++ b/sound/soc/sof/intel/Makefile
> @@ -7,7 +7,7 @@ snd-sof-intel-ipc-objs := intel-ipc.o
>   
>   snd-sof-intel-hda-common-objs := hda.o hda-loader.o hda-stream.o hda-trace.o \
>   				 hda-dsp.o hda-ipc.o hda-ctrl.o hda-pcm.o \
> -				 hda-dai.o hda-bus.o \
> +				 hda-dai.o \
>   				 apl.o cnl.o
>   
>   snd-sof-intel-hda-objs := hda-codec.o
> diff --git a/sound/soc/sof/intel/hda-bus.c b/sound/soc/sof/intel/hda-bus.c
> deleted file mode 100644
> index a7e6d8227df6..000000000000
> --- a/sound/soc/sof/intel/hda-bus.c
> +++ /dev/null
> @@ -1,111 +0,0 @@
> -// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
> -//
> -// This file is provided under a dual BSD/GPLv2 license.  When using or
> -// redistributing this file, you may do so under either license.
> -//
> -// Copyright(c) 2018 Intel Corporation. All rights reserved.
> -//
> -// Authors: Keyon Jie <yang.jie at linux.intel.com>
> -
> -#include <linux/io.h>
> -#include <sound/hdaudio.h>
> -#include "../sof-priv.h"
> -#include "hda.h"
> -
> -#if IS_ENABLED(CONFIG_SND_SOC_SOF_HDA)
> -
> -static const struct hdac_bus_ops bus_ops = {
> -	.command = snd_hdac_bus_send_cmd,
> -	.get_response = snd_hdac_bus_get_response,
> -};
> -
> -#endif
> -
> -static void sof_hda_writel(u32 value, u32 __iomem *addr)
> -{
> -	writel(value, addr);
> -}
> -
> -static u32 sof_hda_readl(u32 __iomem *addr)
> -{
> -	return readl(addr);
> -}
> -
> -static void sof_hda_writew(u16 value, u16 __iomem *addr)
> -{
> -	writew(value, addr);
> -}
> -
> -static u16 sof_hda_readw(u16 __iomem *addr)
> -{
> -	return readw(addr);
> -}
> -
> -static void sof_hda_writeb(u8 value, u8 __iomem *addr)
> -{
> -	writeb(value, addr);
> -}
> -
> -static u8 sof_hda_readb(u8 __iomem *addr)
> -{
> -	return readb(addr);
> -}
> -
> -static int sof_hda_dma_alloc_pages(struct hdac_bus *bus, int type,
> -				   size_t size, struct snd_dma_buffer *buf)
> -{
> -	return snd_dma_alloc_pages(type, bus->dev, size, buf);
> -}
> -
> -static void sof_hda_dma_free_pages(struct hdac_bus *bus,
> -				   struct snd_dma_buffer *buf)
> -{
> -	snd_dma_free_pages(buf);
> -}
> -
> -static const struct hdac_io_ops io_ops = {
> -	.reg_writel = sof_hda_writel,
> -	.reg_readl = sof_hda_readl,
> -	.reg_writew = sof_hda_writew,
> -	.reg_readw = sof_hda_readw,
> -	.reg_writeb = sof_hda_writeb,
> -	.reg_readb = sof_hda_readb,
> -	.dma_alloc_pages = sof_hda_dma_alloc_pages,
> -	.dma_free_pages = sof_hda_dma_free_pages,
> -};
> -
> -/*
> - * This can be used for both with/without hda link support.
> - */
> -void sof_hda_bus_init(struct hdac_bus *bus, struct device *dev,
> -		      const struct hdac_ext_bus_ops *ext_ops)
> -{
> -	memset(bus, 0, sizeof(*bus));
> -	bus->dev = dev;
> -
> -	bus->io_ops = &io_ops;
> -	INIT_LIST_HEAD(&bus->stream_list);
> -
> -	bus->irq = -1;
> -	bus->ext_ops = ext_ops;
> -
> -	/*
> -	 * There is only one HDA bus atm. keep the index as 0.
> -	 * Need to fix when there are more than one HDA bus.
> -	 */
> -	bus->idx = 0;
> -
> -	spin_lock_init(&bus->reg_lock);
> -
> -#if IS_ENABLED(CONFIG_SND_SOC_SOF_HDA)
> -	INIT_LIST_HEAD(&bus->codec_list);
> -	INIT_LIST_HEAD(&bus->hlink_list);
> -
> -	mutex_init(&bus->cmd_mutex);
> -	mutex_init(&bus->lock);
> -	bus->ops = &bus_ops;
> -	INIT_WORK(&bus->unsol_work, snd_hdac_bus_process_unsol_events);
> -	bus->cmd_dma_state = true;
> -#endif
> -
> -}
> diff --git a/sound/soc/sof/intel/hda.h b/sound/soc/sof/intel/hda.h
> index 92d45c43b4b1..a9de6a297b56 100644
> --- a/sound/soc/sof/intel/hda.h
> +++ b/sound/soc/sof/intel/hda.h
> @@ -532,8 +532,11 @@ int hda_dsp_ctrl_init_chip(struct snd_sof_dev *sdev, bool full_reset);
>   /*
>    * HDA bus operations.
>    */
> -void sof_hda_bus_init(struct hdac_bus *bus, struct device *dev,
> -		      const struct hdac_ext_bus_ops *ext_ops);
> +static inline void sof_hda_bus_init(struct hdac_bus *bus, struct device *dev,
> +				    const struct hdac_ext_bus_ops *ext_ops)
> +{
> +	snd_hdac_ext_bus_init(bus, dev, NULL, NULL, ext_ops);
> +}
>   
>   #if IS_ENABLED(CONFIG_SND_SOC_SOF_HDA)
>   /*
>