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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Dafna Hirschfeld <dafna.hirschfeld@collabora.com>,
        Helen Koike <helen.koike@collabora.com>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Sasha Levin <sashal@kernel.org>, linux-media@vger.kernel.org,
        devel@driverdev.osuosl.org
Subject: [PATCH AUTOSEL 5.10 14/36] media: rkisp1: uapi: change hist_bins array type from __u16 to __u32
Date:   Mon,  8 Feb 2021 12:57:44 -0500
Message-Id: <20210208175806.2091668-14-sashal@kernel.org>
In-Reply-To: <20210208175806.2091668-1-sashal@kernel.org>
References: <20210208175806.2091668-1-sashal@kernel.org>
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From: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>

[ Upstream commit 31f190e0ccac8b75d33fdc95a797c526cf9b149e ]

Each entry in the array is a 20 bits value composed of 16 bits unsigned
integer and 4 bits fractional part. So the type should change to __u32.
In addition add a documentation of how the measurements are done.

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/staging/media/rkisp1/uapi/rkisp1-config.h | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/media/rkisp1/uapi/rkisp1-config.h b/drivers/staging/media/rkisp1/uapi/rkisp1-config.h
index 432cb6be55b47..c19fe059c2442 100644
--- a/drivers/staging/media/rkisp1/uapi/rkisp1-config.h
+++ b/drivers/staging/media/rkisp1/uapi/rkisp1-config.h
@@ -848,13 +848,18 @@ struct rkisp1_cif_isp_af_stat {
 /**
  * struct rkisp1_cif_isp_hist_stat - statistics histogram data
  *
- * @hist_bins: measured bin counters
+ * @hist_bins: measured bin counters. Each bin is a 20 bits unsigned fixed point
+ *	       type. Bits 0-4 are the fractional part and bits 5-19 are the
+ *	       integer part.
  *
- * Measurement window divided into 25 sub-windows, set
- * with ISP_HIST_XXX
+ * The window of the measurements area is divided to 5x5 sub-windows. The
+ * histogram is then computed for each sub-window independently and the final
+ * result is a weighted average of the histogram measurements on all
+ * sub-windows. The window of the measurements area and the weight of each
+ * sub-window are configurable using struct @rkisp1_cif_isp_hst_config.
  */
 struct rkisp1_cif_isp_hist_stat {
-	__u16 hist_bins[RKISP1_CIF_ISP_HIST_BIN_N_MAX];
+	__u32 hist_bins[RKISP1_CIF_ISP_HIST_BIN_N_MAX];
 };
 
 /**
-- 
2.27.0