Re: [PATCH v4 2/9] bus: mhi: Move sahara protocol driver under drivers/bus/mhi

On 4/13/2026 4:50 PM, Manivannan Sadhasivam wrote:
> On Thu, Mar 19, 2026 at 12:01:42PM +0530, Kishore Batta wrote:
>> The Sahara protocol driver is currently located under the QAIC
>> accelerator subsystem even though protocol itself is transported over the
>> MHI bus and is used by multiple Qualcomm flashless devices.
>>
>> Relocate the Sahara protocol driver to drivers/bus/mhi and register it as
>> an independent MHI protocol driver. This avoids treating Sahara as QAIC
>> specific and makes it available for reuse by other MHI based devices.
>>
>> As part of this move, introduce a dedicated Kconfig and Makefile under the
>> MHI subsystem and expose the sahara interface via a common header.
>>
>> Signed-off-by: Kishore Batta <[email protected]>
>> ---
>>   drivers/accel/qaic/Kconfig                      |  1 +
>>   drivers/accel/qaic/Makefile                     |  3 +--
>>   drivers/accel/qaic/qaic_drv.c                   | 11 ++---------
>>   drivers/bus/mhi/Kconfig                         |  1 +
>>   drivers/bus/mhi/Makefile                        |  3 +++
>>   drivers/bus/mhi/sahara/Kconfig                  | 18 ++++++++++++++++++
>>   drivers/bus/mhi/sahara/Makefile                 |  2 ++
> Create one more subidr 'clients' and move 'sahara' here:
> 	drivers/bus/mhi/host/clients/sahara/
>
> I'm not sure if we are going to have Sahara implementation for the endpoint
> itself. If so, it should be moved under drivers/bus/mhi/common/.


Thanks for the suggestion. I will create clients directory and move 
Sahara driver here. For endpoint, Sahara driver is implemented in XBL. 
So, its not required here.

>
>>   drivers/{accel/qaic => bus/mhi/sahara}/sahara.c | 16 +++++++++++-----
>>   {drivers/accel/qaic => include/linux}/sahara.h  |  0
> include/linux/mhi/sahara.h
ACK. I will move the header file to include/linux/mhi/sahara.h
>
>>   9 files changed, 39 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/accel/qaic/Kconfig b/drivers/accel/qaic/Kconfig
>> index 116e42d152ca885b8c59e33c7a87519a0abc6bb3..1e5f1f4fa93c12d8ca8fb37633f2f0bee9997499 100644
>> --- a/drivers/accel/qaic/Kconfig
>> +++ b/drivers/accel/qaic/Kconfig
>> @@ -8,6 +8,7 @@ config DRM_ACCEL_QAIC
>>   	depends on DRM_ACCEL
>>   	depends on PCI && HAS_IOMEM
>>   	depends on MHI_BUS
>> +	select MHI_SAHARA
>>   	select CRC32
>>   	select WANT_DEV_COREDUMP
>>   	help
>> diff --git a/drivers/accel/qaic/Makefile b/drivers/accel/qaic/Makefile
>> index 71f727b74da3bb4478324689f02a7cea24a05c2d..e7b8458800072aa627f7f36c3257883aa56f4ce4 100644
>> --- a/drivers/accel/qaic/Makefile
>> +++ b/drivers/accel/qaic/Makefile
>> @@ -13,7 +13,6 @@ qaic-y := \
>>   	qaic_ras.o \
>>   	qaic_ssr.o \
>>   	qaic_sysfs.o \
>> -	qaic_timesync.o \
>> -	sahara.o
>> +	qaic_timesync.o
>>   
>>   qaic-$(CONFIG_DEBUG_FS) += qaic_debugfs.o
>> diff --git a/drivers/accel/qaic/qaic_drv.c b/drivers/accel/qaic/qaic_drv.c
>> index 63fb8c7b4abcbe4f1b76c32106f4e8b9ea5e2c8e..76cc8086825e7949ed756d51fcb56a08f392d228 100644
>> --- a/drivers/accel/qaic/qaic_drv.c
>> +++ b/drivers/accel/qaic/qaic_drv.c
>> @@ -15,6 +15,7 @@
>>   #include <linux/msi.h>
>>   #include <linux/mutex.h>
>>   #include <linux/pci.h>
>> +#include <linux/sahara.h>
>>   #include <linux/spinlock.h>
>>   #include <linux/workqueue.h>
>>   #include <linux/wait.h>
>> @@ -32,7 +33,6 @@
>>   #include "qaic_ras.h"
>>   #include "qaic_ssr.h"
>>   #include "qaic_timesync.h"
>> -#include "sahara.h"
>>   
>>   MODULE_IMPORT_NS("DMA_BUF");
>>   
>> @@ -782,18 +782,12 @@ static int __init qaic_init(void)
>>   	ret = pci_register_driver(&qaic_pci_driver);
>>   	if (ret) {
>>   		pr_debug("qaic: pci_register_driver failed %d\n", ret);
>> -		return ret;
>> +		goto free_pci;
>>   	}
>>   
>>   	ret = mhi_driver_register(&qaic_mhi_driver);
>>   	if (ret) {
>>   		pr_debug("qaic: mhi_driver_register failed %d\n", ret);
>> -		goto free_pci;
>> -	}
>> -
>> -	ret = sahara_register();
>> -	if (ret) {
>> -		pr_debug("qaic: sahara_register failed %d\n", ret);
>>   		goto free_mhi;
>>   	}
>>   
>> @@ -847,7 +841,6 @@ static void __exit qaic_exit(void)
>>   	qaic_ras_unregister();
>>   	qaic_bootlog_unregister();
>>   	qaic_timesync_deinit();
>> -	sahara_unregister();
>>   	mhi_driver_unregister(&qaic_mhi_driver);
>>   	pci_unregister_driver(&qaic_pci_driver);
>>   }
>> diff --git a/drivers/bus/mhi/Kconfig b/drivers/bus/mhi/Kconfig
>> index b39a11e6c624ba00349cca22d74bd876020590ab..4acedb886adccc6f76f69c241d53106da59b491f 100644
>> --- a/drivers/bus/mhi/Kconfig
>> +++ b/drivers/bus/mhi/Kconfig
>> @@ -7,3 +7,4 @@
>>   
>>   source "drivers/bus/mhi/host/Kconfig"
>>   source "drivers/bus/mhi/ep/Kconfig"
>> +source "drivers/bus/mhi/sahara/Kconfig"
>> diff --git a/drivers/bus/mhi/Makefile b/drivers/bus/mhi/Makefile
>> index 354204b0ef3ae4030469a24a659f32429d592aef..e4af535e1bb1bc9481fae60d7eb347700d2e874c 100644
>> --- a/drivers/bus/mhi/Makefile
>> +++ b/drivers/bus/mhi/Makefile
>> @@ -3,3 +3,6 @@ obj-$(CONFIG_MHI_BUS) += host/
>>   
>>   # Endpoint MHI stack
>>   obj-$(CONFIG_MHI_BUS_EP) += ep/
>> +
>> +# Sahara MHI protocol
>> +obj-$(CONFIG_MHI_SAHARA) += sahara/
>> diff --git a/drivers/bus/mhi/sahara/Kconfig b/drivers/bus/mhi/sahara/Kconfig
>> new file mode 100644
>> index 0000000000000000000000000000000000000000..3f1caf6acd979a4af68aaf0e250aa54762e8cda5
>> --- /dev/null
>> +++ b/drivers/bus/mhi/sahara/Kconfig
>> @@ -0,0 +1,18 @@
>> +config MHI_SAHARA
>> +	tristate
>> +	depends on MHI_BUS
>> +	select FW_LOADER_COMPRESS
>> +	select FW_LOADER_COMPRESS_XZ
>> +	select FW_LOADER_COMPRESS_ZSTD
> Why suddenly these configs pop up?


I will remove these in the next version.

>
>> +	help
>> +	  Enable support for the Sahara protocol transported over the MHI bus.
>> +
>> +	  The Sahara protocol is used to transfer firmware images, retrieve
>> +	  memory dumps and exchange command mode DDR calibration data between
>> +	  host and device. This driver is not tied to a specific SoC and may be
>> +	  used by multiple MHI based devices.
>> +
>> +	  If unsure, say N.
>> +
>> +	  To compile this driver as a module, choose M here: the module will be
>> +	  called mhi_sahara.
>> diff --git a/drivers/bus/mhi/sahara/Makefile b/drivers/bus/mhi/sahara/Makefile
>> new file mode 100644
>> index 0000000000000000000000000000000000000000..fc02a25935011cbd7138ea8f24b88cf5b032a4ce
>> --- /dev/null
>> +++ b/drivers/bus/mhi/sahara/Makefile
>> @@ -0,0 +1,2 @@
>> +obj-$(CONFIG_MHI_SAHARA) += mhi_sahara.o
>> +mhi_sahara-y := sahara.o
>> diff --git a/drivers/accel/qaic/sahara.c b/drivers/bus/mhi/sahara/sahara.c
>> similarity index 99%
>> rename from drivers/accel/qaic/sahara.c
>> rename to drivers/bus/mhi/sahara/sahara.c
>> index fd3c3b2d1fd3bb698809e6ca669128e2dce06613..8ff7b6425ac5423ef8f32117151dca10397686a8 100644
>> --- a/drivers/accel/qaic/sahara.c
>> +++ b/drivers/bus/mhi/sahara/sahara.c
>> @@ -1,6 +1,8 @@
>> -// SPDX-License-Identifier: GPL-2.0-only
>> -
>> -/* Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved. */
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.
> Why are you changing the copyright?
I misunderstood the comment from Patch 1 series. Only the copyright 
style needs to be changed. I will modify it in next version.
>
>> + *
>> + */
>>   
>>   #include <linux/devcoredump.h>
>>   #include <linux/firmware.h>
>> @@ -9,12 +11,11 @@
>>   #include <linux/minmax.h>
>>   #include <linux/mod_devicetable.h>
>>   #include <linux/overflow.h>
>> +#include <linux/sahara.h>
>>   #include <linux/types.h>
>>   #include <linux/vmalloc.h>
>>   #include <linux/workqueue.h>
>>   
>> -#include "sahara.h"
>> -
>>   #define SAHARA_HELLO_CMD		0x1  /* Min protocol version 1.0 */
>>   #define SAHARA_HELLO_RESP_CMD		0x2  /* Min protocol version 1.0 */
>>   #define SAHARA_READ_DATA_CMD		0x3  /* Min protocol version 1.0 */
>> @@ -928,8 +929,13 @@ int sahara_register(void)
>>   {
>>   	return mhi_driver_register(&sahara_mhi_driver);
>>   }
>> +module_init(sahara_register);
>>   
>>   void sahara_unregister(void)
>>   {
>>   	mhi_driver_unregister(&sahara_mhi_driver);
>>   }
>> +module_exit(sahara_unregister);
> Use module_mhi_driver().
ACK.
>
> - Mani
>