spi/pwm: fix "uninitialized" warnings

[Livius90]

Fix "uninitialized" warnings which can produced in case of use GCC v12.3.0 with -Wall -Wextra arguments.

[vsergeev]

@Livius90 thanks for the PR. My only concerns are that we shouldn't add *_INVALID states to the end of the enums. What if we legitimately needed to add a new enum member? Generally speaking, we shouldn't change an external API to fix internal warnings.

[Livius90]

@Livius90 thanks for the PR. My only concerns are that we shouldn't add *_INVALID states to the end of the enums. What if we legitimately needed to add a new enum member? Generally speaking, we shouldn't change an external API to fix internal warnings.

It is practical to provide an initialize value for an enum type variable.

https://github.com/vsergeev/c-periphery/pull/51/files#diff-324566633fa8f84c13e8a0e4d2eae73cdf43a89a9db1d75a14cc0bd7b672827bR416

pwm_polarity_t polarity = PWM_POLARITY_INVALID;

What do you prefer to use for initialize an enum variable? If just zero would use, it means it will be initialized for the first enum value. In a more complex code it can cause any issue.

pwm_polarity_t polarity = 0;    /* PWM_POLARITY_NORMAL */

[vsergeev]

It's not practical to put the invalid state after a bunch of valid ones. That's not only confusing, but also breaks the enum for any future additions. I agree with your latter suggestion -- that we might as well just explicitly initialize to 0 (whichever state it corresponds to).

[Livius90]

Do you mean the *_INVALID type should be the first like this?

typedef enum pwm_polarity {
    PWM_POLARITY_INVALID,
    PWM_POLARITY_NORMAL,    /* Normal polarity */
    PWM_POLARITY_INVERSED,  /* Inversed polarity */
} pwm_polarity_t;

What do you prefer now, i can change to use *_INVALID enum types from first position in enum list, or I can just initializing bit_order and polarity to zero without change enums in headers?

pwm_polarity_t polarity = 0;    /* PWM_POLARITY_NORMAL */
...
spi_bit_order_t bit_order = 0;    /* MSB_FIRST */

[vsergeev]

Do you mean the *_INVALID type should be the first like this?

typedef enum pwm_polarity {
    PWM_POLARITY_INVALID,
    PWM_POLARITY_NORMAL,    /* Normal polarity */
    PWM_POLARITY_INVERSED,  /* Inversed polarity */
} pwm_polarity_t;

Yup, exactly. This would have been ideal, but at this point I don't think it's a good idea to break the API.

What do you prefer now, i can change to use *_INVALID enum types from first position in enum list, or I can just initializing bit_order and polarity to zero without change enums in headers?

pwm_polarity_t polarity = 0;    /* PWM_POLARITY_NORMAL */
...
spi_bit_order_t bit_order = 0;    /* MSB_FIRST */

Yeah, this is a good compromise for now. I don't think the comment is actually needed, and it might even be a bit confusing, because the intention is just to give the variable an initialized value rather than set it to the state described in the comment.

[Livius90]

@vsergeev
Done

[Livius90]

@vsergeev
When is it going to be merged?