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[88.127.185.231]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-3a073e5cb16sm10575403f8f.84.2025.04.28.03.07.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Apr 2025 03:07:08 -0700 (PDT) From: Alexandre Mergnat Date: Mon, 28 Apr 2025 12:06:48 +0200 Subject: [PATCH v4 2/5] rtc: Fix offset calculation for .start_secs < 0 Precedence: bulk X-Mailing-List: linux-rtc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250428-enable-rtc-v4-2-2b2f7e3f9349@baylibre.com> References: <20250428-enable-rtc-v4-0-2b2f7e3f9349@baylibre.com> In-Reply-To: <20250428-enable-rtc-v4-0-2b2f7e3f9349@baylibre.com> To: Alexandre Belloni , Baolin Wang Cc: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= , linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org, Alexandre Mergnat X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1438; i=amergnat@baylibre.com; h=from:subject:message-id; bh=kCR/f/rjPnwUXRQOW/h63GEtmBoqR51fZF3et6OR15I=; b=owEBbQKS/ZANAwAKAStGSZ1+MdRFAcsmYgBoD1NJ4dKIwfT8PC10ae4KNPiR9XhLCOKtZ8Q65cCS Hq7l0BCJAjMEAAEKAB0WIQQjG17X8+qqcA5g/osrRkmdfjHURQUCaA9TSQAKCRArRkmdfjHURTPID/ 9smRKUXUNm4htKO++yqvQ8esFin2+J/JciDzLEgSBnf6whPb5fXA6a1FYvw8YpgRf+UaL169HAgwfz jxJaUq2Skp7+/4jjQJ3bo5rPYHZ8f4OJKUDswZkkFi8GZn2cD6vF4J1NQhvAA3M22AAOA8aqfTt6Rm L4Oqvfj7wvpi8K+VmtUwlGHWVVskDdkmrc1JcXP4XEgJfFMDWXY+3rztTtQVJ4y4gZTPtht9xaHzt0 jLcyVWXddxKzTwx2vvsFAsAbg/1TlGbPDoq1uiU8rHV+BKyyLmf0xMfMVTlKEokcIvtWb31Anr3A9+ Rejuu3pPoySXCPOBGzD5Mu9HCuuEK0vLTNmVGzpE7xfMCuaecrLu1sS7Izjr8KHdeTM3dIdks6daDg rVh+vGxTesh3iafop+g8rwlJP4ymeLRlHe3zhiYuZIXwEPlF0hSSyN3NcRerMAPf/ozl1fL9jShgCX iHAlU1a6tWAya7slhYZzfDKSC1eMCs26DQmlvh5vRYwtrBtaMD/krOmYYSt5kxZaK8VpFds9snTjqt Xk/G64Zgii4yF/x9HiERakufKwcprRw8x3GvzQLzxp54LfvTP6KokDcKA+A9YdMDpKSuqalJCtp9N9 uJ2pgvjf6byJeBK5vYL2kEMSy5szeK54qZ3Dj0VoPomM9JPFakaMBO++133Q== X-Developer-Key: i=amergnat@baylibre.com; a=openpgp; fpr=231B5ED7F3EAAA700E60FE8B2B46499D7E31D445 The comparison rtc->start_secs > rtc->range_max has a signed left-hand side and an unsigned right-hand side. So the comparison might become true for negative start_secs which is interpreted as a (possibly very large) positive value. As a negative value can never be bigger than an unsigned value the correct representation of the (mathematical) comparison rtc->start_secs > rtc->range_max in C is: rtc->start_secs >= 0 && rtc->start_secs > rtc->range_max Use that to fix the offset calculation currently used in the rtc-mt6397 driver. Fixes: 989515647e783 ("rtc: Add one offset seconds to expand RTC range") Signed-off-by: Alexandre Mergnat --- drivers/rtc/class.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c index e31fa0ad127e9545afac745a621d4ccbcd5fca28..a0afdeaac270f026734be8785e8ed7e1272b2348 100644 --- a/drivers/rtc/class.c +++ b/drivers/rtc/class.c @@ -327,7 +327,7 @@ static void rtc_device_get_offset(struct rtc_device *rtc) * * Otherwise the offset seconds should be 0. */ - if (rtc->start_secs > rtc->range_max || + if ((rtc->start_secs >= 0 && rtc->start_secs > rtc->range_max) || rtc->start_secs + range_secs - 1 < rtc->range_min) rtc->offset_secs = rtc->start_secs - rtc->range_min; else if (rtc->start_secs > rtc->range_min) -- 2.25.1