linux-kernel - Re: [PATCH V2 2/3] dmaengine: qcom_hidma: add support for the new revision

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Message-ID: <c55ecc2c-332c-e9e6-c74c-3c67fd2ab89a@codeaurora.org>
Date:   Wed, 8 Nov 2017 11:58:42 -0500
From:   Sinan Kaya <okaya@...eaurora.org>
To:     Timur Tabi <timur@...eaurora.org>, dmaengine@...r.kernel.org
Cc:     linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 2/3] dmaengine: qcom_hidma: add support for the new
 revision

On 11/8/2017 11:49 AM, Timur Tabi wrote:
> On 11/08/2017 10:29 AM, Sinan Kaya wrote:
>> +#define HIDMA_MAX_DEV_MATCH 10
>> +
>> +struct hidma_cap {
>> +    const struct of_device_id of[HIDMA_MAX_DEV_MATCH];
>> +    const struct acpi_device_id acpi[HIDMA_MAX_DEV_MATCH];
>> +};
> 
> This seems wrong.  You're defining an array of size 10, but it only has three elements.  And the third element is a sentinel, which is typically used to avoid specifying the size of the array.
> 

It is true that I define an array of size 10. It is just some arbitrary number
with forward thinking. I don't really have to use it to the maximum today as long
as I satisfy the calling conventions.

What is important is that the of_device_match() and acpi_device_match() functions
will stop searching only if they find an empty element. The {} element.

That's the calling semantics of of_device_match() and acpi_device_match().

Besides, C compiler also won't let me put two arrays together like this.

struct my_struct {
	struct some_struct array1[]
	struct some_struct array2[]
}

-- 
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.