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Use proper caution when opening attachments, clicking links, or responding. > > > On Thu, Jun 26, 2025 at 02:22:00PM -0400, Nirujogi, Pratap wrote: >> On 6/26/2025 8:23 AM, Laurent Pinchart wrote: >>> On Thu, Jun 26, 2025 at 12:11:27PM +0100, Kieran Bingham wrote: >>>> Quoting Nirujogi, Pratap (2025-06-25 23:06:01) >>>>> Hi Sakari, Hi Laurent, >>>>> >>>>> On 6/23/2025 5:55 PM, Nirujogi, Pratap wrote: >>>>> [...] >>>>>>>>> I think it can live in the driver for now. Given that the device uses >>>>>>>>> only 8 bits of register address, I would store the page number in bits >>>>>>>>> 15:8 instead of bits 31:24, as the CCI helpers do not make bits 27:24 >>>>>>>>> available for driver-specific purpose. >>>>>>>> >>>>>>>> I'd use the CCI private bits, the driver uses page numbers up to 4 so 4 >>>>>>>> bits are plenty for that. If we add pages to CCI later, this may be >>>>>>>> refactored then. >>>>>>> >>>>>>> That works too. >>>>>>> >>>>>> Thanks for your support. We will add the page number in the register >>>>>> address 15:8 or 11:8 and will update the implementation accordingly in >>>>>> the next version. >>>>>> >>>>> I would like to share the approach we are taking to implement the CCI >>>>> helpers that support page value. Could you please review the steps and >>>>> let us know if they make sense or if any adjustments are needed? >>>>> >>>>> 1: Add new macros to embed page value into the register address. >>>>> >>>>> Ex: >>>>> #define CCI_PAGE_REG8(x, p) ((1 << CCI_REG_WIDTH_SHIFT) | (p << >>>>> CCI_REG_PRIVATE_SHIFT) | (x)) >>>>> #define CCI_PAGE_REG16(x, p) ((2 << CCI_REG_WIDTH_SHIFT) | (p << >>>>> CCI_REG_PRIVATE_SHIFT) | (x)) >>>>> >>>>> 2: Create V4L2 CCI context. Initialize page control reg, current_page, >>>>> regmap etc. >>>>> >>>>> Ex: >>>>> struct v4l2_cci_ctx { >>>>> struct mutex lock; >>>>> struct regmap *map; >>>>> s16 current_page; >>>>> u8 page_ctrl_reg; >>>>> } >>>>> >>>>> 3: Introduce new CCI helpers - cci_pwrite() and cci_pread() to handle >>>>> register read-writes updating the page control register as necessary. >>>> >>>> Out of curiosity - but couldn't the existing cci_write and cci_read >>>> already be used by the users - and then the default behaviour is that >>>> the page isn't modified if there is no page_ctrl_reg - and by default >>>> CCI_REG() will simply have (initilised) as page 0 - so the pages will >>>> never change on those calls? >>>> >>>> Then the users can indeed define >>>> >>>> #define TEST_PATTERN_PAGE 5 >>>> #define TEST_PATTERN_COLOUR_BARS BIT(3) >>>> >>>> #define MY_TEST_PATTERN_REG CCI_PAGE_REG8(0x33, TEST_PATTERN_PAGE) >>>> >>>> and can call >>>> cci_write(regmap, MY_TEST_PATTERN_REG, TEST_PATTERN_COLOUR_BARS, &ret); >>>> >>>> with everything handled transparently ? >>>> >>>> >>>> Or do you envisage more complications with the types of pages that might >>>> be supportable ? >>>> >>>> (I perfectly understand if I'm wishing for an unreachable utopia - >>>> because I haven't considered something implicit about the page handling >>>> that I haven't yet used :D) >>> >>> I don't think we should implement page support in the CCI helpers >>> themselves yet. We have too few drivers to look at to understand the >>> requirements. Instead, I would store the page number in the driver >>> private bits of the 32-bit address (that's bits 31:28), and add wrappers >>> around cci_read() and cci_write() to the OV05C10 driver that handles the >>> page configuration. >>> >>> Once we'll have multiple drivers doing the same, it will be easier to >>> see what requirements they share, and move the feature to the CCI >>> helpers. >> >> Thanks for clarifying. I agree it would be simple and safer approach too >> to handle this way. We will add the following macros in v4l2-cci.h and > > Please add the macros to the driver instead, not to v4l2-cci.h. Once > multiple drivers will implement a similar mechanism we can study how to > generalize it. > Thanks Laurent. That makes it even easier - all changes can be included in the same patch. Its clear now, we will finalize the changes and work toward submitting v4. Thanks, Pratap >> update the existing wrappers ov05c10_reg_write() / ov05c10_reg_read() in >> the driver to retrieve the page and register values to call cci_write() >> / cci_read(). We will add new wrappers too wherever necessary in the >> driver (ex: wrapper for cci_multi_reg_write() on replacing CCI_REG8 with >> CCI_PAGE_REG8) >> >> #define CCI_PAGE_REG8(x, p) ((1 << CCI_REG_WIDTH_SHIFT) | (p << CCI_REG_PAGE_SHIFT) | (x)) >> #define CCI_PAGE_REG16(x, p) ((2 << CCI_REG_WIDTH_SHIFT) | (p << CCI_REG_PAGE_SHIFT) | (x)) >> #define CCI_PAGE_REG24(x, p) ((3 << CCI_REG_WIDTH_SHIFT) | (p << CCI_REG_PAGE_SHIFT) | (x)) >> #define CCI_PAGE_REG32(x, p) ((4 << CCI_REG_WIDTH_SHIFT) | (p << CCI_REG_PAGE_SHIFT) | (x)) >> #define CCI_PAGE_REG64(x, p) ((8 << CCI_REG_WIDTH_SHIFT) | (p << CCI_REG_PAGE_SHIFT) | (x)) >> #define CCI_PAGE_REG16_LE(x, p) (CCI_REG_LE | (2U << CCI_REG_WIDTH_SHIFT) | (p << CCI_REG_PAGE_SHIFT) | (x)) >> #define CCI_PAGE_REG24_LE(x, p) (CCI_REG_LE | (3U << CCI_REG_WIDTH_SHIFT) | (p << CCI_REG_PAGE_SHIFT) | (x)) >> #define CCI_PAGE_REG32_LE(x, p) (CCI_REG_LE | (4U << CCI_REG_WIDTH_SHIFT) | (p << CCI_REG_PAGE_SHIFT) | (x)) >> #define CCI_PAGE_REG64_LE(x, p) (CCI_REG_LE | (8U << CCI_REG_WIDTH_SHIFT) | (p << CCI_REG_PAGE_SHIFT) | (x)) >> #define CCI_PAGE_GET(x) FIELD_GET(CCI_REG_PAGE_MASK, x) >> >>>>> int cci_pwrite(void *data, u32 reg, u64 val, int *err) >>>>> { >>>>> /* get v4l2_cci_ctx context from data */ >>>>> >>>>> /* get page value from reg */ >>>>> >>>>> /* acquire mutex */ >>>>> >>>>> /* update cci page control reg, save current page value */ >>>>> >>>>> /* do cci_write */ >>>>> >>>>> /* release mutex */ >>>>> } >>>>> >>>>> Similar steps for cci_pread() as well. > > -- > Regards, > > Laurent Pinchart